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Hacking the Mantis Elite microscope to control the LED brightness with a 555 PWM circuit.
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Опубликовано:

27 ноя 2012

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Комментарии : 368

@00Skyfox 8 лет назад

I love easy projects like this! They're great for learning the basics of things like timers, dimmers, etc.

@JesusisJesus 10 лет назад

Dave should do a video series called 555 things you can make using a 555.

@badgermost 10 лет назад

Oh yeah!

@jonathanpeden9930 9 лет назад

Bless you, what a great idea...

@JesusisJesus 9 лет назад

EEVblog Hear that Dave, Your People want you to do this series. A million views per video at $300 / million = $166,000 in RU-vid revenue. I would only ask for a meagre 25% cut.

@DerStoeppel 7 лет назад

jesus doesnt need money =]

@ufotofu9 6 лет назад

I like that!

@danaleslie 11 лет назад

Good to hear you're still working on it. One of my favorite EEVblog segments!

@Kezat 11 лет назад

Thanks Dave for this fun little video. It was great seeing you working on stuff in a bit more real time and hands on.

@KPPMt1n7 9 лет назад

Dave...you just screwed Mantis out of doing a $300 accessory light dimmer for their microscope.

@applefanXXX 6 лет назад

What he's actually done is give them the blueprints necessary to steal the idea, manufacture and trademark it, and then take legal action against him. #CapitalismBaby

@thekobaz 6 лет назад

And this video will demonstrate prior art!

@boblewis5558 6 лет назад

They could do all that but "prior art" prevails and their action would fail. Besides, whilst the specific (clever) usage is for the Mantis in this instance the basic circuit exists in probably 10 million posts on the web ... do you think Dave really cares?

@lamjeri 4 года назад

@@boblewis5558 I have seen the second version even on Great Scott's channel. Only difference was that I didn't quite understand the fact that pin 7 is used as an output. 18:50 is quite a jaw dropper for people just learning.

@boblewis5558 4 года назад

@@lamjeri a quick look at the internal circuit block diagram of a 555 would explain that confusion. BOTH pin 3 AND pin 7 are effectively output pins. Pin 7 being labelled "discharge" doesn't mean it cannot be used as an "output" pin because internally it is basically just an open collector of an NPN transistor, which when switched on provides a discharge path to ground for the timing capacitors. Pin 3 conversely has an output drive circuit which has its own "pull up" internally, hence the lack of need for the external pull up when used as the "discharge" pin. A clever use of basic understanding of the internals to "reuse" the chip in a clever component reduction. An engineering solution to the ever present "bean counters'' desire for cost saving, no matter how trivial! It might surprise people starting to learn, but even engineers with decades of experience can be surprised by novel uses of a circuit because someone has realised the "detail" and how it can be used alternatively. A classic example is the use of 3 logic inverter gates to produce an oscillator. Not something that might easily occur to someone just starting out in electronics but very old hat to someone of experience.

@grundell2930 5 лет назад

This is one of your best vids Dave

@Nono-hk3is 5 лет назад

Thanks for showing the traditional version of the circuit before optimizing it. That's very helpful.

@TheExplosiveSheep 11 лет назад

Definitely the video I have enjoyed the most from you this month.

@bernym4047 Год назад

Dreat educational project and demo of making a PWM circuit from 555. Many thanks.

@elboa8 11 лет назад

Thanks Dave, my favorite type of video.

@WhitentonMike 11 лет назад

I like the idea of having each side's LEDs adjustable in brightness so you can get some control of the direction the lighting is coming from. An XY pot would be friggin sweet. Run the stick along the diagonal for equal overall brightness and off diagonal for fading from one side to the other. User friendly as heck!

@jaypae7002 9 лет назад

Informative, clearly explained, outstanding as usual. I have 555 ckts I still use that I made about 15 years ago. I'm now encourage to dust off my scope, meters, etc and build the LED dimmer, which I need... .

@3deeguy 5 лет назад

Thank you for posting. I didn't notice until the second day that BOTH sides of the potentiometer were connected to power through a 1K resistor.

@SarahWattCA 9 лет назад

Cool stuff. My preference would have been to use circuit 1 with an N-channel MOSFET as a low-side switch. Circuit 2 was a clever solution though and I never would have thought of it.

@bernym4047 Год назад

That would be my preference also. Thanks.

@QuadfishTym 11 лет назад

Love how elegant and small the final solution is. Considering doing something similar with a logarithmic pot to get a variable boost converter.

@scknight 11 лет назад

Super cool project!

@drobinson2299 9 лет назад

I had subtitles on for a few of these videos, as I didn't have my headset around. The way you're voice is automatically made into subtitles had me cracking up give it a try some time, just turn captions on when watching a video back. I wanted to do something exactly like this myself, I'm going to copy the final circuit and wire it up to my own mantis. Amazing they did not include something like this for such an expensive price of equipment!

@NGinuity 9 лет назад

Thanks Dave, I've seen a lot of your stuff and keep finding ways to implement things from videos you do. I think I am going to use a slightly modified version of this to make a dimmer for the under-cabinet LED strip lighting I'm installing in the kitchen. On a barely related note, I'm going to buy one of those t-shirts for my wife merely so I can comment on how nice the threshold and output pins look when they're cold :-P

@ConjUK 11 лет назад

Great vid and hack Dave, love it.

@georgemarkuly8180 2 года назад

Very good. I like coming of pin 7 . Used that pin in a simple 555 time base circuit on a very simple scope and a 0.1 out from the transistor. .

@jasoneyes01 11 лет назад

Brilliant Dave

@EEVblog 11 лет назад

Yes, I was thinking that, but the wires are paralleled inside the optic head, so you'd have to have a separate pot and circuit inside each LED half. It would be pretty ugly.

@Hydrogen4Health 11 лет назад

thank you for sharing your knowledge. it really helps a beginner like me.

@Mrsrtheflyingmum 11 лет назад

Good Vid. Dave. I was using your first Bread Board design and changed it to your second design, as its for a differant use I have differant resistors but thanks the new board works much better.

@TheExplosiveSheep 11 лет назад

Loving the ChestCAD Dave!

@mrtriac3024 7 лет назад

Be aware that NE555's output is not rail to rail, especially in logic 1 state. A resistor(let's say 1kΩ) betweeen base-emitter(BD136) would greatly improve transistor's switching time and would reduce collector cut-off current. A maximum limit current resistor(330Ω or more) at discharge pin(7) or at the wiper is a good idea too.

@gkdresden Год назад

This is not relevant for the CMOS 555 timer versions.

@EEVblog 11 лет назад

Ground bounce from inductance of the test lead. No ground clip on CH2 (so uses CH1)

@Trevs-Shed 11 лет назад

Thanks Dave. I will certainly get down to modding mine. And yes, different types of LEDs could well be useful. In fact vision engineering can supply different led banks. Not sure how much they cost though.

@ArtoPekkanen 8 лет назад

This video was very informative for a beginner like me :) Thank you so very much!!! :)

@aerofart 11 лет назад

Nice one, Dave. Would love to see more episodes like this one where you actually MAKE stuff!

@DolganoFF 9 лет назад

This T-shirt sould have DaveCAD written under the picture!!!

@SnowyOwlPrepper 7 лет назад

Lovely. Could a bypass switch be used to get that additional 100 lux.

@rahuljathar4430 3 года назад

You should connect a 1k resistor between those two diodes opposite to trimmer. I built the circuit on breadboard and it works fine but when i made it on pcb as a prototype, my smd 555 chips worked good for several minutes and then stopped working. I blew 2 chips and then i searched some formulas, and came to know that the capacitor on pin 6 is getting charged through the resistor, diode and potentiometer and discharging through the diode only directly to ground through an inbuilt transistor on pin 6. Due to very low resistance on the discharge path, when the duty cycle is at maximum, the capacitor is discharging in a very short time and a lot of current is flowing through inbuilt transistor which will eventually blow the chip making it unusable. I dont know how long the dip version of chip lasts with this circuit but the smd chip will blow instantly. So add a 1k resistor in the discharge path!!!

@glenmartin2437 5 лет назад

Good video. Thanks for the instruction.

@logitech446 11 лет назад

Hi, Dave, great video as usual. You can omit the 220R too, replace the BD136 with a IRF520N. Did this works great.

@TheBadFred 11 лет назад

PWM doesn't change the voltage/amplitude like a voltagedivider/pot, it changes the fequency - is like switching on and of very fast. The brightnes is determined if "the switch" is longer on or off (longer on -> brighter and longer off -> less brighter)

@photocanonn 11 лет назад

great video!

@EEVblog 11 лет назад

Yeah, it was basically real time. It's a video I could have shortened a lot in editing, but I figured there was more value in the real-time stuff.

@nyghost9991 10 лет назад

Great video!!!

@PIXscotland 9 лет назад

Would be nice if this could have dimmed one or the other side independently so you could get "side-ish" lighting. That's sometimes useful for component recognition and adds a bit more 3D depth to the image.

@Jones12ax7 8 лет назад

+PIXscotland I think it's just a matter of build 2 units and placing one each side. Good luck

@edwinedmondson6440 9 лет назад

Excellent Example!!

@Pukkeh 2 года назад

Nice, simple solution. A fancier solution might use a logarithmic pot, since the human perception of brightness is more or less logarithmic.

@MagiKnightOne 8 лет назад

Nice video Dave!! I applied your circuit as a comparision between Analog PWM vs. Microcontroller PWM. Pretty interesting behaviour using constant voltage source. I can reach 26% as minimum and 96.76% as maximum. I do not why, but, pretty intersting thoug. Thank you.

@WhitentonMike 11 лет назад

I don't quite know enough about the math to explain it here but the values are based on a formula that determines the values for the fewest parts that will give the most complete spread of values. The formula is also used to determine things like what currency values a country should have for the best use of resources and transaction efficiency.

@UberAlphaSirus 11 лет назад

KISS, just change the existing lm317 to a voltage reg with the pot and be done. the led's have individual resistors up to the plug packs voltage for there max draw. Unless you wanted to do a 555 tutorial that is ;). Take care Dave, love your vids.

@CanadianMang 11 лет назад

Dave, I think it would be great if you made more videos that were like tutorials for electronics beginners and/or intermediate. For example, teaching us how an adc works, or maybe beginner embedded electronic design, or maybe even teaching about microcontrollers, what a dc/dc converter is. Stuff like that.You have so much knowledge that you should share with us.

@bloomtom 11 лет назад

Oh wow, you left LEDs as the steering diodes. This is a lazy hack with a legendary level of purist utility in the design, I love it. "We don't really care, we just want to get this thing working." - Dave Jones

@TheBadFred 11 лет назад

That's the hacker's spirit I wanted to ignite with my proposal of the PWM device in between the Mantis and the power supply.

@zainaabdin 4 года назад

Super dave....no doubt

@EEVblog 11 лет назад

That's effectively what a dropper resistor does, converts the constant voltage into a known constant current.

@gkdresden Год назад

You can always save this pull-up resistor in 555 timer astable multivibrators by using its output pin to control charging and discharging of the capacitor. You can also save the base resistor by use of a p-channel MOSFET for switching of the LEDs also from the output pin.

@jesperahman738 11 лет назад

I'd like to see the voltage out of that LM317 when you use the dimmer! I suppose it's jumping all over the place.

@Saurocksall 11 лет назад

u have given me many ideas..... Thanks...

@KB1UIF 11 лет назад

Nice and simple , like it !!!

@DiveSafariNZ 8 лет назад

Thanks Dave, I'll give this a go later.

@EEVblog 11 лет назад

Err, it's a 0.1uF bypass cap... And the regulated 9V input (minus the LM317 drop) limits any possible maximum voltage. Nothing to worry about.

@jarrinson29 8 лет назад

Very good, but I have one question, because use 2 leds and non-conventional diodes, such as 1N4007 or the like, or failing that the typical 1N4148?

@EEVblog 11 лет назад

I need to re-spin the board for a different form factor.

@UberAlphaSirus 11 лет назад

What might be good also it to be able to switch one side of leds off so you can get shadows, can be handy some times.

@EEVblog 11 лет назад

Yep, same thing. So called because it "drops" voltage.

@basemgamal622 7 лет назад

can this PWM handle high amp's or i have to replace some parts ? EEVblog

@h0lx 9 лет назад

The light mater enclosure seems quite common, I have a thermocouple thermometer in one of these

@jrrymiller 11 лет назад

Dave, When I do this circuit I connect the pin 4 to pin 5 this eliminates the need for the small cap and makes for an easier PC board layout.

@kckc9245 3 года назад

Hi. I have a question how can i use the LM555 too get a square Wave on the output with a music sound input and adjustable speed. Thank you 👍

@mariodistefano2973 3 года назад

Hi Dave, why don't you use a mosfet instead of the PNP transistor?

@caddyguy5369 Год назад

Any ideas to use a 0 to 5v potentiometer to dim RGB without messing up the color mix? I am expirimenting with a PWM fan controller for testing, but if I'm thinking right for the final install I may be able to use the Pam signal from the factory computer that is controlled by the dimmer knob.

@dalenassar9152 4 года назад

Hey Dave!!! I have been looking for a good push-pull 555-based circuit for a LONG time! On your DaveCad drawing, would I get this if I connect a load to your BD136 output (to source current) and pin 3 (to sink current)? a couple hundred mA at 40kHz to 50kHz should be sufficient.

@4dirt2racer0 Год назад

i noticed the transistor had casing molded around the back of it, does that ever interfere with the grounding? like do u ever have to sand them to get a more reliable connection? or am i totally wrong about that even.. does it Not also ground thru the back? i know, random ass question.. im just curious

@GogogoFolowMe 9 лет назад

Hi Dave, just a quick question : I don't understand why the frequency is changing in the circuit #2. In fact, when you adjust the pot in one direction, it lower the resistance to load the condensator and higher the res. to discharge it. And vice versa. The freq. must stay the same, why not ?

@Inesophet 8 лет назад

Wow learned more!

@johnkerley4152 10 лет назад

I ca'nt find a lot of information on this type of pulse circuit. So I was wondering how well it works. I know that there are some lights that use this type of drive system. I wonder if the circuit you have would work well outputting 1 amp?

@adamlumpkins2000 11 лет назад

good one dave!!! Do more hacks!!!!!!!

@killer1479 11 лет назад

hi, i enjoy watching your videos,and also some of the circuits you make... would it be possible for you to make a book of circuits and the diagrams and maybe release it for the ipad ^^ ?

@insylem 7 лет назад

I know this is an old video, but I want one of those 555 shirts. How do I get to the Zazzle store? Is it still available?

@DemiGod3 4 года назад

Can this chip NE555 use to drive a mosfet for the backlight circuit in a led tv? If your circuit can be used, what would be the output to connect to the gate of the mosfet and what value gate resistor? I think I should say it’s a Chinese tv but the PWM chip is defective so I just want to direct drive the mosfet for the backlight.

@LuckyImExil 11 лет назад

No worries, I'm not red-green colorblind and the light green is pretty similar to the yellow for me, too ^^ That's something that has been bothering me with quite a few scopes I've used in the past.

@CoolDudeClem 11 лет назад

Good old 555! So versitile, I wonder if it could be used in a switch-mode power supply?

@-Graham 10 лет назад

Hi Dave (and everyone!) This is rather inspired, I have seen this circuit a few times (including hackaday) and now i know where it came from. Would it be a simple mod to invert the output so we get ~10% min to 100% brightness? Thanks!

@dumle29 11 лет назад

"should" - no "could" - yes if he wants to share his knowledge, it his choice, and would be a great gift from him. It's not his obligation tho.

@circuitsandshortcuts 4 года назад

Skip the 1K resistor, and swap pins 3 and 7 on the 555. Use pin 7 as the output (it's open-collector) and pin 3 (push-pull) to drive the steering diodes to the sides of the pot.

@johnkerley4152 10 лет назад

I was wondering, what do you think about the use of such a circuit to make an LED put out more light by pulsing higher than normal forward current at a low duty cycle and high frequency?

@aqib2000 11 лет назад

Nice video. I'm looking to purchase a power supply for my laptop repairs. I've found 2 at a very good price both are 0-30v 0-5amp. However I believe they are Constant-Current. Would current limiting be better? Plus is there a method create an add on to manipulate the CC to current limiting seeing as the maximum current set would readily be available anyway.

@alexanderkuhn2298 Год назад

What would be the best way to control the pulse width using a microcontroller? Would the pot have to be a digital pot in order to work properly or can a microcontroller DAC simply output a voltage to this circuit somehow?

@WayneJohnsonZastil 11 лет назад

Very nice use of 555 and nice hack. Should should contact them and donate the schematic so they than add it to next version or maybe charge or get free one.

@TheLuvvgunn 11 лет назад

Would adding a couple of separately controlled UV or RGB led(s) help identify "scrubbed" chips by changing contrast?

@insylem 7 лет назад

Also, since it was only 1/2 amp current, why not just put the pot on the 317 and make it vairy the current linerally?

@trafrellik7350 10 лет назад

The video explains it. The P.S. drives a constant current device, so more resistance would simply increase the voltage (across the pot) and deliver the same current to the LED's. A PWM is the perfect answer to this situation, although a non-inverted output would have allowed a higher PWM cycle (10% - 99.9% is better than 0% - 90% for LED control).

@johnconrad5487 8 лет назад

the circuit is simple but to keep the frequency fixed u need a different circuit i.e. with two resistors and no diodes in the discharge path. or why did u not use pin 5 which is meant to do pwm?

@hefonthefjords 11 лет назад

if you want to see some car LEDs in action, watch some of top gear's tests of the newer ferrarris and lamobs. they all have obvious PWM in their LEDs when you see their highspeed cam footage in the road tests. it's pretty interesting to see it show up in slow mo like that.

@hefonthefjords 11 лет назад

i was referring to frequencies of "flashes" due to the PWM signal, not colour frequency of light. for example, there are times where i have been in office buildings and been able to "see" the flashes of the flourescent lights overhead. obviously its fast as hell but sometimes it's perceptible to me.

@jcglessner 5 лет назад

Can I use the n channel transistor to drive a p channel transistor?

@johnkerley4152 10 лет назад

I thought I saw the frequency swing swap when the 555 circuit had the last modification. It was at first lower frequency at higher duty cycle and then it went to higher frequency at higher duty cycle.

@hefonthefjords 11 лет назад

question dave; what is the lux output of the two LEDs in the 555 circuit? how much of the missing 2% of the total lux output of the circuit do they make up? if you were to integrate the whole circuit into the mantis and make those LEDs white could that help make the whole thing more efficient in terms of lost original output?

@electroGoal 3 года назад

Can we make buck or boost circuit with feedback using two 555 ic. Please reply

@ImaginationToForm 11 лет назад

Hi, Did have a question on the leds. Do they just look like they are lit at the same time since the voltage changing direction so fast? Thanks.

@BustaniTech 11 лет назад

Good info. I have a question. If I wish to create a 5KHZ PWM signal (+/- 3 %) over the full range of the pot sweep achieving the full 5% to 98% change in duty cycle what combination of Resistor and Capacitor value do I need to use in your design. Thanks.

@EEVblog 11 лет назад

Did you watch the whole video?

@onurolce 11 лет назад

I agree with you %100. Also I wish to Dave starts to teach about Microcontroller programming such as open source Arduino...

@UberAlphaSirus 11 лет назад

Not only that, you have the balls to make them make it standard issue :D

@MariaEngstrom 11 лет назад

The thing that amazes me the most is that the manufacturer of the microscope did not include the dimmer function. Would not have affected the manufacturing price by to many fractions of Dollars I imagine. It could even have been used as a selling point. Love the solution. :)