Dual Display Hack - ebay special to Differential Current

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In an effort to evaluate simple and accurate display for my various Power projects a little while back including my analogue DC load , I found and bought some panel meters from aliexpress here
www.aliexpress.com/item/Blue-R...
on initial examination hey seemed to have issues when used for all but the basic systems but......
on receint examination I discovered that they use a seperate differential input ADC chip to read the current that has markings "CA2P" and had shorted the negative input to the 0V rail of the power / Voltage sense input with a zero ohm value resistor negating its differential ability and in the processess limiting its flexability.
I will show you here how to Hack it back to a differential input and how I integrated it into a DC Load
Now these displays have a whole new lease on life...

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Опубликовано:

11 июл 2024

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Комментарии : 168

@apollorobb 2 года назад

The SOT23-6 device is a MCP3421 18bit ADC

@DJDevon3 7 лет назад

Nice hack. Love how a simple pinch can make these more accurate too. Great video.

@FlyingShotsman 9 лет назад

Well done, Peter; nice hack. I'm impressed with how accurate that meter turned out to be. I'll have to buy one and fiddle around with it myself. / On another topic, I wanted to thank you for the videos about building your workbench. I copied your design and now have a very sturdy 3' x 8' bench with shelves above and below. Lots of space to build stuff! Cheers.

@DutchBigEd 3 года назад

Thanks for the explanation on how to measure the current differential. I am in the proces of building a dual powersupply for a testrig for eurorack synthesizer units and now I think I can build it the proper way 😀👍🏻

@robertcalkjr.8325 9 лет назад

Nice job, Peter. Thanks for the video.

@teddysoft 3 года назад

I have finaly found a instructional video on this specific topic, that is spot on how to understand the princible of this kind of meter. You have earn my subscipsion to your channel 💪.

@TheBreadboardca 3 года назад

Thanks for the feedback and support

@edinfific2576 4 года назад

That little "display meter" is more accurate and precise than most handheld DMMs on the market.

@leogenic 7 лет назад

Good tips!! thanks for sharing.... and 2 thumbs up for the great presentation!! :)

@michaelhompus2475 8 лет назад

Nice hack. After watching it I ordered a few of these units too to replace the analog indicators in my bench supplies. I must say though that in the last part of your presentation, where you discuss the DC-load, you seem to become a bit sloppy and rather brief in explaining things. I fear that a number of interested viewers can't follow that anymore. Just dropping a simplified schematic without further explanation about the basic workings of the DC-load probably leaves a lot of viewers puzzled (as I was before a second view of that part). Anyway, I appreciate your effort to spread knowledge about electronics. People do not seem to realize anymore that that (and other technologies too) have become basic necessities in our present world. To some of the other commenters I'd like to say: try searching and tinkering a few minutes longer.... I did find identical panel meters within 2 minutes (even at a better price), so don't bug Peter with silly questions and appreciate that he sparked your interest. The fun of electronics as a hobby is finding out things yourself isn't it?

@TheBreadboardca 8 лет назад

+michael hompus Thanks for the feedback, I will keep it in mind for future videos Peter

@cccyberfamilydk 8 лет назад

Great hack. Nice video

@CharlieTechie 4 года назад

Just what I needed, thanks.

@glenemo2079 7 лет назад

Brilliant - thanks Peter - a great and useful hack and extremely well presented. I picked up one of these "ebay" panel meters which has exactly the same wiring configuration but only 3 digits... I wanted to do your differential hack which will be perfect for a project I'm working on but unfortunately the I can't locate the 0 ohm surface mnt resistor... - ie. the circuit brd has a very different layout... I tried to find the actual module you used but the links are no longer active - so can you; - help me figure out where the 0 ohm is on my unit (I could send you a close up photo of the board or - tell me how/where I can buy the same unit that you used / hacked... Many thanks

@jamest.5001 6 лет назад

what about the high current ones? with external shunt. for like 500amps. I need one. but would like to know more about them before I buy one. for my 24v 5kw inverter plus multiple DC loads. so I can read total draw from the bank. great and informative video.

@elboa8 9 лет назад

Nice. Thanks Peter. Why do you not have more views/subscribers???

@arrowstheorem1881 7 лет назад

Excellent contents!!

@RobB_VK6ES 9 лет назад

Great little hack Peter, well spotted. I wonder if a similar mod could be made with their higher current versions? Looking for just such a meter right now.

@TheBreadboardca 9 лет назад

Rob B probably, I would think the main difference is simply where the shunt is located, but no guarantees untill you have one in your hands and have a look

@donaldfilbert4832 5 лет назад

I love these dual volt/amp meter modules - but have always run into the limitation for its application due to the common ground between the volt measure leads and current sense leads. This modification is great !! I just wonder why the manufacturers don't manufacturer the module with the current sense floating in the first place??

@TheBreadboardca 5 лет назад

too easy to burn them out if you wire it incorrectly is probably the reason, they dont want to be replacing them all the time.

@NavinBetamax 4 месяца назад

It's been 8 years on since this video was uploaded. None of the wise guys in the electronics world who have seen this and commented here till today has pointed out a mistake made while measuring resistance in the milli-ohm range.............Our Great Guy here is A Shunt to the actual resistance being measured , because his finger tilps are in contact with both prongs of the multimeter. !!!! So much for the electronic buffs here !

@TheBreadboardca 4 месяца назад

The part about 14 mins in is were i see myself "Shunting" the Shunt resistor, considering the value of the shunt is in the milli ohms (0.025Ohms) the human body resistance is something in the kOhms (even 10K is very low for a body) will have negligible impact on the reading ( 1/Rt = 1/Shunt + 1/body ) = 1/0.025 (40) + 1/10,000 (0.0001) = 1/40.0001 = 0.0249999ohms. I hope this is self explanatory in response to your comment. Am I shunting the value... yes, significant in any way... no. if this was a resistor of several K then it will be more significant and as its value increases, the affect is more so, but as I said, in this case it is not relevant. I do appreciate your comment though and thanks for the opportunity to educate a few viewers that may have thought the same thing and just not said anything.

@NavinBetamax 4 месяца назад

@@TheBreadboardca Thank you for this response....all ways good to hold bare wire when taking ANY reading ( wether negligible difference in read value than the exact value ). is what is stated in your reply. So...how about measuring milli-volts just your way !!! Next...upscale and try wall outlets........Bare finger tips, Of Course !!! Education ???

@TheBreadboardca 4 месяца назад

@@NavinBetamax Your twisting my words ?, measuring an un powered milli ohm resistor using your fingers to keep the wires on the probes is not at all the same as sticking your fingers in a live socket, if the person doing the measuring is not aware of basic safety etc then they should not be using the meter.

@NavinBetamax 4 месяца назад

No….no twisting of any words of yours by me here……Straight up you are doing it right. Please forget I ever said anything here. Peace !!!

@TheBreadboardca 4 месяца назад

@@NavinBetamax No Problems

@sarinaguillen6895 6 лет назад

Thank you very much for this vídeo.

@TheBreadboardca 6 лет назад

Your welcome, hope you found it educational or helpful

@rafaelquintero9029 5 лет назад

What MOSFET and operational integrator you use to do so? thanks for the video it's really clear information

@TheBreadboardca 5 лет назад

this ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-vd5IBFFjnOc.html and this should help :) ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-rh32ylmlz-A.html

@tomkiska2614 6 лет назад

If I do this hack can I use different Gnd or - for meter pwr and Amp circuit? I believe the - blk small wire and - blk large wires are same potential.

@TheBreadboardca 9 лет назад

Thanks for the Link eccentric, When I looked, searching CA2P nothing came up :( so I appreciate you sharing and yes it looks exactly like the one I was observing, now I have the info, perhaps I will hook up my I2C protocol analyzer and see what its doing with it. It looks like a good chip to use in small projects and is probably very cheap to be included in a product like this

@raimundtrierscheid6318 8 лет назад

eccentric is right; it is the MCP3421. Look at this link: www.eevblog.com/forum/beginners/43-000-count-voltmeter-from-10-bit-adc-how/

@eded8045 5 лет назад

Nice vid! I presume both segment displays are identical ? but as Im waiting for my delivery I wondered if there is a simple hack to reverse the colors because Im more naturally inclined for Amps to be red and Volts blue or is it simply desoldering both segments and swapping them around for the color change?

@TheBreadboardca 5 лет назад

De-soldering is the only option I can think of, though I am not sure if the blue is a coating or actually blue LEDs in which case the forward voltage drop will be different

@aberakadabra1285 5 лет назад

Cool dude ; ) I bought a digital ammeter 3 wire job , unfortunately I need a 'isolated' power for the screen display , or it reads the volts then adds the amps to that :/ the whole idea of using it was to ditch the battery . Maybe I can check the black wires like you did ; ) Do you think maybe a simple circuit could fix this problem in order to power the display from the source that is being measured ?

@cwgreenley 8 лет назад

Did you take any data to show the difference between before and after the hack?

@johnhopkins6260 6 лет назад

DSN-VC288, however, my example has no internal shunt... In lieu of the shunt, a R075 SMD.. also Versions I have (with Shunt) do not have "CAP" device nor 0 Resistor... Also have seen 2 solder holes upper-left while looking at the back, shorted together at turn on, "resets".

@stevetobias4890 4 года назад

I just go t one of these in the past few days for a similar purpose but it has an external shunt and I am getting some weird readings. If I connect the voltage wires (red & black) to 5v and connect nothing else, I get a reading of about 0. 56 A and no voltage reading. I'm thinking it is a dud

@alex-r2pi 4 года назад

After seeing this video I ordered myself one of these modules in the hope to be able to modify it. Unfortunately it is a different layout. Besides an anonymous 20 pin µC it consists of an LM358 an M5333B (probably voltage regulator) and a tiny tiny 6 pin SMD marked with 3157 (ADC?). No quick win ...

@juanolmosmendoza5361 2 года назад

Hello, how have I just purchased an HP 3468A multimeter, and it is somewhat out of calibration as it happens with all these models, it requires calibration since over time the battery with which they retain their parameters is discharged because it is digital, however doing tests Simple it shows that if it reads voltages almost equal to those obtained with a cheap multimeter or perhaps better, but I am interested in tuning it, it has some video on this for repair, maintenance and calibration

@RT-wh6yr 7 лет назад

I was excited by this hack and did some testing and promptly burned out a meter. Reading the ADC data sheet, we see that the inputs can't exceed VDD, so that might be it. In any case, it ruins my use case. My use case: a 5V and 12V supply. Low side current monitoring won't work as electrons won't know which path to take. Does anyone know of a high side solution/suggestion?

@davey2k12 7 лет назад

thanks bro I need to do this Cus I just got a dc one 0-99v and 0-50amp but its counting down from 50amp lol but I've got 12v bat powering it and it's measuring my li ion at 52v ish lol

@tonbovee5486 7 лет назад

Thanks for this smart dual display hack your diagram can the A meter also be placed between drain and + without damaging the meter special at higher Voltages ?

@TheBreadboardca 7 лет назад

probably not as the common mode voltage can easily be exceeded and therefore damage the electronics.

@beatlessteve1010 Год назад

I have been trying to find the schematic for this because I have a blown SMT resistor next to the small connector and I can't read the value

@quixotic010 4 года назад

Thanks for the video. What is the minimum current resolution? Can it read 1-10 mA? Thanks.

@edinfific2576 4 года назад

Apparently, it is 0.1mA.

@supreetyadav5021 27 дней назад

A version of this with hall effect current sensor would be cool

@Nathan1975Liggy 2 года назад

Can it be hacked to take the amp reading from the + rail instead of the - Rail? If not what volt/amp meter will allow me to read the amps from the possative rails?

@TheBreadboardca 9 лет назад

For those looking for an equivilent of the one I hacked, I found one, a company interesed in me reviewing some of this products sent me a display module among several other products and it is exactly what you need www.gearbest.com/development-boards/pp_134241.html, it says 3Amps but will go over 5, just the shunt gets a little warm which is probably why my origional once dissapeared from the listings and the all now say 3A.

@Hagar76a 4 года назад

Found this while looking for circuit and wiring diagrams for these meters. I want to separate the unit power from the sense because the all seem to be common positive and have the shunt on the negative. I am installing in a vehicle so I wish to keep common ground... Not possible in the normal state. I have 2 more recent versions that don't seem to have a 0R that I can remove. They also have a small wire 2 pin connector and a larger wire 3 pin connector, so they are arse about a bit. What else can I look for to allow me to make common ground?

@Hagar76a 4 года назад

Also, you did not show how you did or would actually wire the meter into your circuit. To measure voltage and current separately would require 4 wires, but there is only 3. How did you achieve this?

@satishkumar-gg5fm 4 года назад

Great Sir 👌👍

@TheBreadboardca 4 года назад

your welc0me

@kennedy6971 4 года назад

I'm obviously no electrical genius. Doesn't it just make sense that a zero ohm resistor shouldn't exist on anything? If its zero ohms then there's no resistance? That must not be correct.. I am a tinkerer.. Electric bike builder.. This guys stuff is always A++.. He's a great teacher, I'm the poor learner

@TheBreadboardca 4 года назад

not a poor learner, your someone willing to ask when there is something they dont understand, so a good learner :) there are several reasons for zero ohm resistors, the first being the most common (In my opinion) 1. provide a simple jump over a trace that would otherwise be difficult to route, in the past a builder would use a wire link, now they just use a zero ohm resistor 2. provide a simple way for configuring a chip that requires a high or low for some purpose, perhaps an address, a mode of operation etc 3. used in cases where different values may be used for say calibration, and the zero ohm resistor is just part of the math so to speak :) why SMD zero ohm resistors rather than wire jumpers, well there way cheaper and can be installed using the same pick and place machines that are doing all the other component assembly there are probably plenty of other reasons, but i think you get the idea. In this case with the ameter the zero ohm resistor ties the input of the opamp to ground thereby setting it to a single ended operation, with my example in this video of removing it, allows the device to work in differential mode and gives more flexibility in how you measure the current but you have to be more careful not to exceed the common mode voltage ratings of the circuit. Hope that all helps

@kennedy6971 4 года назад

@@TheBreadboardca thank you. Yes it helped me get a better picture of the entire circuit

@vladimirpetrovic1316 5 лет назад

Excellent video. Great Analysis and explanation. Do you have an idea of how to read AC 100A meter down to a mA. It is AC V/A meter model YB4835VA. I tried running several turns of the primary wire through it but got accuracy within 100mA. Many thanks V

@TheBreadboardca 5 лет назад

You would need a meter that will change ranges or have a very large dynamic range (0.001%), thats almost 7 digits and certainly more than a 16bit ADC if you wanted to do it in a single range. If your ok with changing ranges then you could build something or buy something like a Panel Pilot meter that can have its ranges changed under script / program

@johncoops6897 Год назад

You can convert an Ammeter into a MilliAmp meter by psssing ONE THOUSAND TURNS through the CT.

@marcelocmj6680 8 лет назад

Peter sorry for my questions and this.will be the last !!..it is not 10mah bit 10A .. the bike has a hub brushless motor and at least 15A i expect to flow and wantwd to measure without the need to carri a bulki shunt (i barely know what it is) in the bike while I ride...i bought 8 units and what i wanted to know if i use below 10A (not riding fast.or in big slopes) will i be able to have proper readings of amps lets say +/- 200mah error using stock.hardware? (no shunt is coming on that dx sku)

@TheBreadboardca 8 лет назад

+Marcelo Cmj The SHUNT is already mounted on the back of the display but is only rated to about 3A continuous, I found on mine I could push it to 5A for short periods but it was getting quite warm. Cutting off the shunt and replacing it with small wires to an external shunt of a lower value will allow you to get your 15A range better, the shunts are not necessarily big when their value is low. You would need to know the current shunt value in order to calculate the new ones value though Oh, and yes I did realise your talking about 15A, not 15mA. :)

@davidabbott7194 7 лет назад

Hello Peter Great video! I have the same meter, but i can only measure the current from the DC load negative terminal... Will this hack help me to measure the current from the positive terminal? If not you know how i can do it? Thanks

@TheBreadboardca 7 лет назад

probably not, the supply to the ADC is probably 3V3 and the + rail would take it way out of the common mode range and fry it (As I found out when my main current sense resistor got fried in my Phoenix Contact PSU review...

@rob6676 7 лет назад

tried doing this hack to a couple meters that are very similar to yours. only had to scratch a trace. however hooking it up, my current (blue) shows '----' meter still works but i think the ground side of the current meter also needs to be referenced from the meter. looks like the 'ca2p' isnt grounded anymore. I was trying to measure volt/current on battery and solar system, but not very successful. 1. plugged red/black to both meters from battery side. meters power, but no longer getting data. shows '----' on current side (blue) 2. plugged in current where one side is grounded. meter shows current (blue) Still working on it.

@TheBreadboardca 7 лет назад

I think you're correct. The current measurements common mode voltage will probably need to still be contained within the supply range of the ADC, and also most of these meters are low side measurement for the current shunt relative to the 0V line. On my testing the purpose was to eliminate the drops due to wiring etc and from that perspective it worked well.

@Nathan1975Liggy 2 года назад

I would like to use one of thease (I have the 10A ones) on a meanwell type 30A PSU. The PSU already has 3 shunt resistors going to the output of the PSU. Couild I remove the shunt from the meter and connect via some wires to the shunts already on the PSU Boared output for a upto 30A reading oin the meter?

@TheBreadboardca 2 года назад

probably not, the ones on the PSU will be tied into its feedback loops for protection, regulation etc. you would be better off simply adding the meter outside of that, it may be possible to wire the load to eliminate the efffect of your shunt, although its affect would typically be minimal anyway.

@Nathan1975Liggy 2 года назад

@@TheBreadboardca Many thanks buddy

@originalmianos 9 лет назад

Sbas 357 cheapy ti differential spi d2a?

@Domingues3D 9 лет назад

Nice. Thanks. Sorry to bother you, but I can't find a panel meter like your's. The one that you specify is only a 3A on max scale. Where can I find one?

@TheBreadboardca 9 лет назад

André Domingues No Bother, I just looked and even the one I bought from the same link has changed i did find this one www.aliexpress.com/item/Cheap-version-4-bit-DC-0-33V-3A-Red+Red-Dual-LED-Display-0.28-Digital-Ammeter-Voltmet/32240698328.html and this one www.aliexpress.com/item/Red+Red-Dual-LED-4in1-Digital-Thermometer-18b20-Power-meter-Ammeter-Voltmeter-voltage/1861736635.html but not 100% sure if you can do the same hack as I dont have either, the second one does look to be the identical base unit though

@Domingues3D 9 лет назад

Peter Oakes Thanks for the fast response and the time spent to help me. I will check it out. The second one looks like your's. Thanks again Great videos. Continue making more.

@thewhizard 6 лет назад

I got 2 of these think the pot on the back for adjusting currant reading is bad. any idea the resistance of the pot is. think I should be able to solder in a replacement.

@TheBreadboardca 6 лет назад

I dont think I have any with a POT, mine was all done in software, and required pressing the button on the back

@edinfific2576 5 лет назад

If it's a DSN-VC288, the trimmer for current adjustment is around 20k ohms, but I would add more resistance there as it is not enough to set it correctly. Another 10-20k is needed.

@marce002b 8 лет назад

sorry i would like to know what to do to have a 0 to 15A current range reading ok? i have just bought 8 units@!!

@TheBreadboardca 8 лет назад

+marce002b The current range in these is limited in software so while changing the current shunt to give a different scale, you may have difficulty moving the decimal point

@TOM-cj4ct 3 месяца назад

The little sot23-6 ic is a mcp3421 from microchip

@TheBreadboardca 3 месяца назад

Thank you, I appreciate the info (As will any interested viewers)

@peddersoldchap 2 месяца назад

Hi. I bought one of these volt\ammeters. I has a voltage adjustment pot, but no amperage adjustment, although in the description it said it had both and it even had pictures of the PCB showing both pots. Ironically, the voltage measurement is quite accurate but no the current. Is there any way I can increase the accuracy of the ammeter?

@TheBreadboardca 2 месяца назад

often the volts range is directly measured by the CPU on the board, with a divider network of course, the adjustment will just tweak the divider ratio. The current if often measured by a small ADC external to the CPU, it is programmed by the CPU and unless your able to re-program the device is pretty much fixed. Having said that, the SHUNT (Small piece of thick wire usually ) could be adjusted by filing or soldering to its surface to adjust its value. The adc is measuring the voltage across the shunt . It is often the case were the description of a device does not match the reality of what you received. especially if there made and bought from "Overseas" at a budget price.

@peddersoldchap 2 месяца назад

@@TheBreadboardca Ha! Mine doesn't even have a metal shunt like the one on the video. Of course, in the pictures it has a shunt (lol). The one I have has one big 16 pin chip (unmarked) and a voltage regulator. There's a "big" R018 smd resistor near the ammeter connector, though. Could that be the "shunt"?

@TheBreadboardca 2 месяца назад

@@peddersoldchap Yes, most lightly it is. it would be under 1ohm in most cases and the more current it is rated for, the lower this value would be to keep heat dissipation down, most lightly it is in the milli ohms range..

@peddersoldchap 2 месяца назад

@@TheBreadboardca So, if I want to adjust the ammeter, I should replace that resistor with one of a different value?

@Karl_Levine 3 года назад

First of all - great job and video, thank you for this. Now for a remark : wouldn't this hack also fix the biggest con with these, ie, that these meters can only work wired as low side current meter? Wouldn't your hack enable you to use it on the high side now as well?...

@TheBreadboardca 3 года назад

you would have to be aware of the effects of common mode rejection and exceeding the max input voltages of the op-amp. In theory yes that can work, in practice it depends on how it is wired and what chips are used, without a schematic, it would be difficult to tell without reverse engineering

@Karl_Levine 3 года назад

Not so easy then you say. Thought it'd might open the door to use an isolated power supply on the meter, and hooking the current measuring side in line in series on the positive of the load. Would be great if you can test this!

@tommyhash3202 6 лет назад

Question. Does it make a difference if they're 25mAh shunts vs 75mAh shunts or are they interchangeable?

@TheBreadboardca 6 лет назад

I will assume you mean a 25A shunt vs a 75A shunt, no they won't be interchangeable as the voltage developed across them for the same current will be different, therefore the meter will read wrong if you change the shunt to a different value. With these values you must have an external shunt ?, it is also possible that the meter is already able to read the higher range and just the shunt is different but that is less lightly.

@tommyhash3202 6 лет назад

Peter Oakes Sorry, I should have clarified. If I buy two kits with external shunts, both statr 75mAh shuntd but one is a 100Ah shunt and the other is a 500Ah shunt, will either of those show the correct readings?

@AlienRelics 6 лет назад

There is no such thing as a mAh or Ah shunt. Those terms mean milliamp-hour or amp-hour, and are used as a measure of charge capacity in batteries.

@TheBreadboardca 6 лет назад

ok, but give Tommy a break, I already feed back on that and we all know what he really means. :), we just need to inform him of the right appropriate terms , some of my viewers are beginners, some are more advanced and my channel is all about helping folks learn in a safe way

@ncmynz 6 лет назад

Tommy Hash 0

@fardellp 6 лет назад

Does anyone have experience of these digital meters in an RF environment? e.g. when monitoring voltage and current applied to a 10watt amateur radio transceiver?

@johncoops6897 Год назад

You cannot use this to measure the RF output. However you asked if it can be used to measure the power TO the transceiver, in which case it will be perfectly OK since that is just DC.

@georgegonzalez2442 6 лет назад

Only glitch, if the inputs go directly to the chip, they're unlikely to work below ground or above Vcc, a silicon limit as you would be back-biasing the substrate or tub diodes.

@TheBreadboardca 6 лет назад

you are certainly correct there, this will provide differential but not outside of the supply limits and as there is no series limiting resistors, somewhat easy to destroy the ADC in a fault situation so one needs to be careful in wiring this up. and has a limited use as in it is not suitable for all scenarios

@crocellian2972 7 лет назад

What is that 2 channel scope on shelf 2? I want it.

@TheBreadboardca 7 лет назад

The two channel one on the very top shelf is an ATTEN 1102 (100Mhz 2 channel), the one on the middle shelf is a Tektronix MDO3054 with ALL the bells and whistles. 500Mhz, 6GHz Spectrum, 4 Chan Analog, 16 Chan digital, AWG, Protocol Decode etc, one scope at each end of the cost spectrum.

@peteride-kostic737 3 года назад

My model is unfortunately different. For the current sensor, it uses an op-amp (fed by 3.3V) configured as a single ended amplifier so with one side of the shunt connected to the V+ side of the op-amp (via R1) and the other side connected to the common PCB ground (so no magic zero ohm resistor in my case). The V- side of the op amp is connected to the PCB ground via a resistor (R2) and to the output of the amplifier via a third resistance (R3) that provides the negative feedback. For some reason that I do not understand (probably to compensate the offset) , V+ is also connected to +VCC of the op-amp (so 3.3V) via R4 which is actually very high (3.3 M ohms). My question is how to modify the operational amplifier set-up to switch from a single ended mode of operation to a fully differential one. The objective is to have the possibility to connect one side of the shunt to the + side of any external power sources whatever its voltage is (even if is > 3.3V) and the other side of the shunt to the positive side of the Load (the negative side of the Load being tied to the negative side of the external power source). I tried a few mods without success as the op-amp went into saturation systematically (even when the op-amp was fed by the same power source than the load so it shared the same +VCC). Thanks for your advises

@TheBreadboardca 3 года назад

Some times it is just easier to make your own, there are examples in my videos of current sensing using special but inexpensive chips to perform both highside and low side sensing, you would use an Arduino, Raspberry PI or some other microcontroller to read it and display.

@marcelocmj6680 8 лет назад

ok i have no shunt at all....should i use to measure 0 to 10A with no troble?

@TheBreadboardca 8 лет назад

+Marcelo Cmj I think the internal SHUNT will get too hot if you pump in 10 Amps and the display may give an error over 3 or more amps, this depends on what software has been programed into the unit, For 10-20A I would suggest getting a current meter with an external shunt or specifically rated for that amount of current

@augustinconstantinescu5765 4 года назад

I'm a beginner and I want to build a power source! Can you send me a wiring diagram? Thanks!

@saxy1player 9 лет назад

What is the voltage range that can power this thing? (what Vcc does it require)?

@TheBreadboardca 9 лет назад

saxy1player Basically the power for the display can be anything a standard surface mound little 3V3 regulator can take, typically about 4V right up to 24 to 30V based on the one I used

@saxy1player 9 лет назад

Peter Oakes cool, thanks for the info - I'm building a supply and was just wondering if I would need any special supply, but I guess I can just use my 5V one

@patrickholcomb9628 8 лет назад

in the last 4-5 minutes you explain where you put the components in schematic form (very well i might add). i am having difficulty with practical application (putting schematic to real life components). i am new to this but could follow...kinda :-/ . Could you possibly break it down with actual components? I am very visual, and although your schematics are well put together, it still looks like a rat maze to me. i apologize for my ignorance. if need be i can give you a rough idea of what components i am working with. also, i am a little confused about the wiring on my unit. wire coloring is different. power to display is easy enough (red/black), but the shunt and test wires are confusing me. i have blue (pos to shunt i think), green (neg to shunt or test) and yellow as test positive..i think. their order of colors from power to test side are: black, red=power; blue, skip slot, green, yellow. i know without looking at circuitry it might be difficult to give me the answer to this, but maybe you can hypothesize from your/other units.

@pollydor07 6 лет назад

THANKS

@sirifail4499 4 года назад

Both sides of the sense resistor must be “close” to GND. They can not be below GND, nor can they both be much above ground. Ask me how I know.....

@TheBreadboardca 4 года назад

Oh... I know how ;)

@johnhopkins6260 4 года назад

DSN-VC288? (i.e. WHICH chinese "e-bay special" ??) searched for YB5135D...

@jd957 3 года назад

Can someone update this showing how to hack the new dual digital so the negatives are not common?

@californiakayaker 4 года назад

looking for a meter that would differentiate between positive and negative current and give you indicators.

@rogerbarton497 2 года назад

I gave up looking - I use two similar to these connected back - to back, one reads current in one direction and vice-versa.

@californiakayaker 2 года назад

@@rogerbarton497 Well what the heck, that works, and they aren't really expensive.

@johnhopkins6260 5 лет назад

$1000 DVM... wow.... came across similar "E-bay specials": DSN-VC288; two variants: 10A version where wire shunt is visible, 1A version (R075 SMD, in lieu of shunt)... wanted to use this to create low resistance test box (+/- 3.7xx Ohm and +/- 0.7xx Ohm), utilizing LM317 as current regulator... via 12.5 ohm in "adjust" circuit, set to 100mA... do the math... viola! Was trying to figure out if thin yellow current sense connects to "VCC IN" @ LM317... or "output" @ LM317... 5VDC "wall wart" for meter power (thin Black, thin Red). At $10 bucks a pop, trying not to roach too many.. also something similar with 10A version of DSN-VC288 and LM338. test box is for checking motorcycle wiring (over switches) and generator field/stator windings.

@TheBreadboardca 5 лет назад

Sounds interesting, are you posting the build process / testing ? also the multi-meter is only about 500 - 600$$ CDN assuming thats what your referring to, I do have an expensive one too (Truevolt 7.5 Digit) but thats not in this video and is way more than $1000 I think.

@secod2022 2 года назад

Hi where dld YOU bougt this voltmeter

@necbd8893 Год назад

what's solution 20amp current measure using this ckt

@johncoops6897 Год назад

The solution is to NOT use this circuit, as this is only for 3A to 5A.

@bp9293 3 года назад

Hi mine did not come with a shunt. Does it need a particular value?

@TheBreadboardca 3 года назад

depends what you bought, if it is about 5 - 10 amps then its probably built in, look for what looks like a heavy gauge wire loop on the board

@bp9293 3 года назад

@@TheBreadboardca It has no shunt built in. It is a 100amp version.

@bp9293 3 года назад

@@TheBreadboardca I was thinking of using flattened copper pipe. what millivolt range do I need? I am a bit lost. www.ebay.co.uk/itm/DC-100V-100A-Voltmeter-Ammeter-Blue-Red-LED-Dual-Digital-Volt-Amp-Meter-Gauge/283621092127?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649

@TheBreadboardca 3 года назад

@@bp9293 If the one in the link is the one you have and the view is the same as the first picture then it already has a shunt built in, its the thick wire loop right near the connector

@TheBreadboardca 3 года назад

@@bp9293 But I dont think that image is right or the add itself, there is no way the connector will handle 100V 100A safely, the one you need should more look like www.ebay.co.uk/itm/DC-10A-50A-100A-Voltmeter-Ammeter-LED-Dual-Digital-Volt-Amp-Meter-Gauge-M5X9/112553871462?_trkparms=aid%3D1110006%26algo%3DHOMESPLICE.SIM%26ao%3D1%26asc%3D225114%26meid%3Ddae0a925e82e4e93ae6b09c8acc3e0bb%26pid%3D100623%26rk%3D1%26rkt%3D5%26mehot%3Dpp%26sd%3D283621092127%26itm%3D112553871462%26pmt%3D1%26noa%3D1%26pg%3D2047675%26algv%3DDefaultOrganic%26brand%3DUnbranded&_trksid=p2047675.c100623.m-1 I dont know what the mV is at the current rating for the meter... sorry

@nintendoplaystation1 6 лет назад

Does anybody know if this is hack is also working with a DSN-VC288?

@TheBreadboardca 6 лет назад

It is a very different display, I did find this that seems to show a partial valid schematic, based on it I would say no, not easily www.drive2.ru/l/475415634784551097/ have fun

@nintendoplaystation1 6 лет назад

Thank you for answering my question. That's sad, I planned to used them with my PWM motor controller, but for that I need to connect both grounds, without that the display would switch off everytime I switch the power off. I can't really see in the schematic how the grounds are connected, maybe I can just scratch the connection?

@TheBreadboardca 6 лет назад

If you simply want to keep the meter on even when the supply is off (The measured Voltage), I think that is already supported. The Supply for the meter is separate to that of the sense for voltage. It only has a common ground. Now if you are needed to switch the ground, not the + then yes, that would not work so well. If you are able to get the shunt removed from the meter it may be possible to do it though as now the ground will only be for the meter, but you would have to be careful.

@nintendoplaystation1 6 лет назад

Thanks, I will try. I have the 50A variant with external shunt.

@TheBreadboardca 6 лет назад

well that will make it easier :)

@marcelocmj6680 8 лет назад

shame ok...i wanted to use it for an ebike while riding...i think at least 15A would be a must.....thks

@TheBreadboardca 8 лет назад

+Marcelo Cmj As I said, you could ignore the DP and add a parallel shunt to scale it to 1.5A equivalent, that would still resolve to 10mA which sounds plenty for your application. Or cut off the shunt and put your own in but close to the battery rather than the meter so it is not wasting cable loss

@sirifail4499 4 года назад

Now if anyone knows how to measure high side current white these meter?

@TheBreadboardca 4 года назад

While nothing is really impossible, this is one were the effort would not justify the gain, it would be far simpler to buy a high side meter or make your own with a high side current chip and a volt meter or microcontroller

@sirifail4499 4 года назад

theBreadboard I’m making a dual voltage supply. If the outputs are grounded together, I don’t know how they will share, and accurately indicate each current. I have two ideas I’m looking at. Get the separated voltage and current meters. For high side current. Get a 5v isolated supply. Put ground of the isolated supply on the “live wire”, and the positive and negative of isolated supply go to power the meter. Put the shunt in line with the output (positive). Wire this “live” wire as the “pseudo” return for the load. Shunt wires 1. Just before shunt up in load wire. 2 just after shunt. Power. Two sides of the isolated 5 v ==== This might work with combined meters The other involves a g=1:1v/v high voltage input op amp. Idea: remove shunt, leaving pads intact. Get a small piece of vector board and wire to it. In Red, black, yellow of voltage meter. RED AND BLACK wired intimately with the shunt. Add the diff amp across the shunt. Now we the ability to high side measure current without being constraint by the death if the AGC.

@tablatronix 8 лет назад

Nice hack, too bad these ebay meters all use these crappy blocky led segments

@peterowens290 8 лет назад

Sorry, starting with your diagram, I got lost. My dual meter is not exactly like yours anyway. More important how many folks will feel comfortable removing the minute resistor? I clear connection (hook up) diagram would of great help. Your verbal descriptions are not suitable.

@TheBreadboardca 8 лет назад

+Peter Owens Can you provide a link to the one you have, perhaps I may be able to find a diagram for it and point you int he right direction for yours