This video will describe how to build a simple PWM circuit and how it works. A CD4093 Nand gate logic IC will be used instead of the commonly used microcontroller.
Thanks a lot 0033mer, this is exactly what I've been looking for: gate driving a low-side N-channel FET with inexpensive BJTs. There are so many sources of questionable info on the net that I doubly appreciate and trust your content. Thanks again from Waterloo, Ontario.
Nice circuit to handle loads of a couple of amps or more. For loads of and amp or less I use a 555 timer since it is a more compact package ( 8 pin DIP ) as opposed to the 4093 ( 14 pin DIP ). The 555 can also drive the mosfet directly without the two transistors used here. I've built several of these in the past to mount directly on cooling fans for some projects. You can add a couple more components to make the pwm temperature controlled.
No need to use a microcontroler to make the frecuency constant, you could do a triangle wave generator (Like a 555 IC) with a fixed frecuency and then use a comparator to convert the triangle wave to a square wave with variable pulse width. Basically a VCO (Voltage Controlled Oscilator)
can you provide the 555 timer link that shows such a clean 0-100% square wave duty cycle? Also that is any better at maintaining frequency? no dig man just... can you?
i have a bad backlight circuit in a tvset, it uses the AB3350CP, im not getting any PWM to the chip the mosfet that drives the out put to the led arrays isnt been driven as it currently im just at 46volts, with oscillation it should be at 120volts. Is there any way to drive the chip or just turn it on fully?
Sir do you know how can I control pick up coils out put for distributors? I need some thing to control duration of pulses ore the 4 pin gm ignition module Im experimenting lot with engines so I wuld like to build me self variabel controled ignition timing . Im simply useing multipel engine types so I need some thing that does that task . Im even useing dual coils and dual 4 pin gm ignition modules only problem I have only 1 pick up coil so I need to ajust that for ich coil corectly.
I really love the explanation of this video but can you mr tell me how you biased the output voltage here?..like did u use 12v by a transformer or by a function generator? Can you also tell what is the input and output of the oscilloscope in your circuit?
The circuit was powered by 12 volts DC from a bench power supply. The waveform on the scope was monitoring the the PWM signal feeding the gate of the MOSFET.
I am looking to build a simple fixed 50% duty cycle circuit like the one shown at 4:36. Where would I look to determine what value resistor and capacitor I need? For context I am trying to roughly halve the RPM of a DC motor, but I won’t need to adjust it afterwards.
Check out this site. It has a 50% duty cycle PWM 555 timer circuit with formulas for component values. www.electronics-tutorials.ws/waveforms/555_oscillator.html
A freewheeling diode is used to clamp inductive voltage spikes that occur when you remove power from an inductive load. Check out this video for a detailed explanation. ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-LXGtE3X2k7Y.html
Wow!, thank you so much for your educative video's. I enjoy watching them since I never got educated on this subject. Why didn't you use a 555 timer for this circuit. I thought that that is the first pick to make for building a PWM circuit? But I like this one, I just don't have this IC. And can you tell me where your name 0033mer comes from or stands for? Thanks again for sharing your knowledge. I appreciate it :)
Thanks for the feedback! I have used the 555 for PWM circuits with the same results. I used the CD4093 in this video because it is very versatile. It can be used as an Inverter, NAND gate, AND gate, Schmitt trigger and also an audio gain stage. You can also parallel them for more output drive. The CD4093 is very common and easy to obtain. I have used this circuit in other videos: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-h1aA5gfeU34.html My channel name 0033mer was my work employee number which I had for many years so it is something I will never forget.
@@0033mer Nice, thanks for answering :) I just ordered some CD4093's, so I can have some fun with it in the future. I also asked you a question in another vid which was: what is the tool exactly called with which you can sculp your varoboard with? It is a sort of hand grinding tool and I want to order that also for my first pcb project :) since I only prototyped on breadboards sofar (and I cannot locate it on-line....) And I gave it some thought how you came up with that name. And since I am dutch the 3 is here pronounced as drea (drie in dutch), so I thought it was a coded name for drea-mer :) And I will sure have a look at that other video.
Good luck on your projects. I sent a link for the boring tool in the other video but here it is again. Here is a link: www.rpelectronics.com/r22-0239g-veroboard-cutting-tool.html
I wish you had showed the motor when it started up. You said it starts slow, but by the time you show it it is already going fairly rapidly. I don't know what you mean by start "slowly". I ask this because I am trying to start a motor very slowly, and not having much luck. It is off and stays that way until a critical voltage is reached, then it jumps to a slow speed. Do you have any other videos that show a slow start ?
To achieve a slow start you need a microcontroller controlled PWM circuit. A DC motor needs a large current to start compared to the lower running current because of back EMF generated by the motor when running. The initial torque to turn the mass of the armature when starting also increases startup current. When you apply your PWM signal it waits until the the pulse widths can give enough current to start the motor and once started the motor will jump to the PWM speed. You need a smart kickstart signal generated by a microcontroller. On startup give a initial 30% kick PWM signal, as the motor starts up bring the PWM down to desired slow speed.
Easiest way would be to use a microcontroller (Nano) to generate the PWM output and a pushbutton switch connected to a GPIO pin to set the desired PWM duty cycle.
My career involved engineering communication links (voice and remote control) using UHF/VHF radios and fiber optics. Check out other videos on my channel that will show related projects. ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-WT9xWyLK-Ic.html ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-R_UQa3gXbwY.html
@@0033mer Thank you for your response. Did you receive formal education for electrical engineering beforehand? Or are you self-taught/On-the-job experience only? I can appreciate your substantial knowledge and experience, it is inspiring! Perhaps you may decide to do a short bio video so others can learn about your background too!
@@0033mer I'm sorry I forgot to include this we not allowed to use microcontrollers or any software programmable devices. Is there any other option you can recommend?
You could use a thermistor as the temp sensor in a voltage divider circuit feeding the non-inverting input of an opamp. A triangle waveform is fed into the inverting input of the opamp. As the temperature changes, the PWM output of the opamp will change which will control the motor speed.
Yes, Schottky diodes are preferred for free wheeling applications because they dissipate less energy during switching. The motor I was using draws 50 mA so a 1N4148 with a forward current spec of 300 mA works in this application. I usually indicate 1N4148 or 1N4000 series (1N4005) to be used because most people do not have a Schottky in their parts bin. For high current inductive drive applications a Schottky diode would be the best choice.
Absolutely NOT, there are much simpler ways doing so - you get triac, you get potentiometr and one resistor maybe, and viola, you control exact moment [voltage of AC] triac opens and close, if current of gate is too small, wont ever open, if it's high enough will be kept opened all the time, you can even use photoresistor to dim light automatically, PTC thermoresistor to make temperature regulator, MOSFETS in general are for low voltage high current applications, transistors are for higher voltage applications ~100V or so, thyrystors for DC to AC conversion and triacs (basically two thyrystors merged in silicone) are for high voltage AC, IGBT mosfet driving bipolar output are for high voltage, high speed DC
You could use a potentiometer to control the brightness of a low current LED, but is not practical or efficient to control large current devices. When the pot is stopping the motor it is taking the full current and voltage so the power dissipated is high which will heat up the potentiometer.
I don't know if you still monitor or reply to your post but I will take a chance. I am trying to run a Treadmill motor by its motor control board. I do not have the user interface so I have no way of sending whatever commands ( I suppose the commands means that knob you adjust in your bread board). So I been messing with the motor control board trying to figure things out. And after lots of messing around I have reached this point There is a 20 pin ribbon harness. 10 pins each row. I managed to touch two wires which read 12 volts. In doing so, a LED light that said PWM came on. On another 3 wire pin not part of the 20 pin harness, I read a little over 2 volts between two of the pins. Connecting those two, another LED came on and it said "sense" I checked the motor output and it seem to read 18 volts at all times. There was another two pin connector which read 5 volts. When I connected that pair, a bunch of lights came on, the DC motor light, the AC motor light and another light by the 20 pin harness and a nice loud click was part of this rascal pair of wires. With all that going on. I connected a small DC motor to see what it does and before doing so the voltage output was still at 18 volts so I figured my little DC motor won't be on fire as the main motor for the Treadmill can handle to 110VDC. There is another two pin connector that read 12 volts. I was just messing with it just like I was messing with the rest, touching and seeing if something will melt or get caught on fire or not. Once comfortable then I just connect thing for good. So I connect this pair and nothing. But all of a sudden the motor began to get going and I kep it connected. The motor sped up for 30 seconds or so and then came to a stop. Dang I said to myself. the motor was cool to the touch and no fires on the control board. So I unhooked thsi 12 V pin and then connected them back again, the motor didn't move. Frustrated I started nibbling at the pins, connect, disconnect, nothing. Then all of a sudden when I would touch the pin with certain rate, the motor would turn. But soon I gave up because I couldn't figure out the pace. The motor would go and not go. So in conclusion. what do you read in all that has been mentioned. Total three, 2 wire pins ( one being in the 20 pins ribbon harness, pwm LED) and the other two outside of it on the board. And one 3 pin harness ( sense LED). If I get PWM frequency generator from Amazon having 4 wires coming out of it. Can I control this and make it work to run the Treadmill motor and if so where would the 4 wires go? Thanks in advance if I get lucky getting an answer.
Without a schematic and wiring diagram it's hard to tell what's going on. The controller board takes 120VAC and converts it to DC to run the motor. PWM is used to control the speed. So you have two wires for AC input and two wires for DC output. A pot with 3 wires on the controller board will control the speed. Look for a MC-60 controller board on eBay and check online for wiring schematics. ctmprojectsblog.wordpress.com/2018/09/29/treadmill-dc-motor-mc-60-controller/
@@0033mer So the potentiometer just plays a role in the supply of voltage or what? would think it can not control off and on and pulses pwm role.. After all it is just a variabel resistor which has nothing to do with sending pulses... Of course I am confused. Messing around that board caused by sheer obsession I cracked the code so to speak and am able to run the motor. I thought I had put the link and or the motor controller board, I guess not. This is the controller, (asm-mef1j-3b control board). It is for Vision T9700HRT Treadmill. There is not a place anywhere on the internet that I could find even the slighest clue as to its schematic, wiring diagram or whatever it is called. The two pins that showed 12 volts that I was messing with I connected a potentiometer 50K. I shorted the middle one to the low side of it.. or whatever it is called so I ended up with two wires to hook it to the two pins. The two pins that showed 5 volts, I simply decided it was the switch to turn on whatever that was not turned on when I supplied AC power to the board. So I shorted that two pins, I figured that means the switch is flipped on. The 3 pins that showed 2 volts between two of them and the third showed nothing, I figured that is just for looks, as in like some odometer in a car. I figured the car does not need the odometer to work for it to run. At least not yet until someday they will make sure they will do that too. Nonetheless I didn't shorted circuit that you could say. ===================== What I ended up finding out that once everything is hooked up and turning that potentiometer, nothing would happen as it describes what I stated my original inquiry. Well, for some reason it is because it takes some time for the entire board to really charge up you could say. And that means the LED light for the DC output finally turning on. The reason it came on the first time around when shorted that two 5 volts pins is because the circuit was supplied with AC voltage for at least half hr as I was just figuring things out. And up on shorting that two pin, the DC out led had come on instantly. Then I found out that if I turn the motor by hand ( but I have to wait about 5 minutes or so) after everything is on, only then that LED for the DC out turns on. Then by turnng the potentiometer the motor gets going totally perfect. It appears that 50K is the just the sweet size for it as far as I am concerned. I don't have to turn the potentiometer almost half way to get the ball rolling and when it is at the low position the motor stops and I can run the motor as low as 50 RPM as I see it. So the only thing that I sit and wonder about is how that two PWM pins in that ribbon cluster work because now I am messing with another controller. It is Percor controller. Another Treadmill obsession. There are two separate pair pins that I know of, between each pair I noticed about 5 volts. And the motor does the start and stop thing, the same pwm behavior as the previous above controller. However I found one pair and not exactly next to each other but one over. The voltage between that two is 2.5 volts. When I short circuit that the motor takes off like a rocket and when I used a potentiometer, same thing. Nothing happend and then finally it takes off as I turn it half way basically. When I used a voltmeter to see what happens with the two pins, the DC out pins for the motor jumps from reading 2 volts to 60 and the same when I turn the potentiometer half way, It is either nothing or 60 volts basically, no higher and no lower. And that is my uneducated, crazy stupid way of figuring things out. I do have a sense about them flip flip, sr latch inverter, logic this and that, nand and or stuff which I don't like the way it is taught at all. Why? Because across the board everybody just throw abbreviation at you just as they supposedly begin to explain the basics. I don't even know what to call it. [[ By the way both of the above controller board have them that plastic potentiometer thing you have. It doesn't do a thing as far as I see it in either one to controll anythng. It is like it was set at some 10 oclock position I noticed on both. I am looking at your sit up and your microcontroller sr lach thing to see how that potentiometer causes change with PWM frequency or whatever they call it. It appears that there is a reason there is a place for a potentiometer ( an analogue item) even in a PWM circuit. I guess it must be better than pushing on some button up and down to cause on and off time. And all the games that can be played]] One is put in a position in a position to know what those abbreviation are plus what they mean, whatever the meanings maybe. They start out with abbreviation and not with the actual principle first. For instance instead of starting at some base phemomenon to arrive at 0 and 1. They start at 0 and 1. They make 0 and 1 as the principle itself. To me not that is totally wrong and untrue but even more than that. Even if someone somehow comes around and use the term off and on. Or 0 and 1 volt.. or whatever, even that is false, outright false. I know it is because I have followed up to its core. The so called square waves they shove down my mouth is not off and on. And I will even go futher, it is not even right to say it is two voltage state for those who really want to be pecise as if they really know it to be the actual case. No it is not. If the state as actually off and on, it won't be square waves period. The word wave can not be used. The fact that the word wave is there already means that there is background voltage. So I tell them, " got you". If it was truly off and on there will be an absent of any line, a total discontinuity between two of the peak square shape and not continuous line and furthermore it is false to show straight lines, with respect to verticle line on the voltage Y axis. As in reality the voltage drops in time and not out of time segment. So all lines ( if not tweaked) on the oscilloscope in fact must and should lean to the right as X is the time axis. And I will even count hysterisis, so call schmidth latches or whatever they want to call it. Anyway I went all over the map and wore myself out.
You have some engineering problems in your design my friend. The free wheeling diode should handle the same amount of loading current at the flyback and 1N4148 is not rated for these loads under test. The capacitor at the power supply line for decoupling is meaningless for a value of 0.47uF since the larger 470uF will cover the effect even though the frequencies you used. Also, for the same reason you mentioned about the switching diodes for the duty cycle control, you should not use very high values like 1MOhm because it will not operate the diodes properly so x100 greater than the R value will be the max.
Yes .. you are correct. The free wheeling diode should handle the same current as the load. The small gear motor draws 50 mA and the rating of a 1N4148 diode is 200mA continuous forward current with a surge current of 2 Amps. It is good practice to use a small value non electrolytic in parallel as shown because electrolytics become inductive at high frequencies. I mentioned a lower value pot resistance as the 1 Meg pot was all I had at the time. This was a simple circuit targeted for beginners to show what they could run into and how to correct if they run into problems.
0033mer ... The free wheeling diode current should not be considered as the load current itself but the load switching device rating as the real load is changing and varying according to work load. Also, we should not consider the max. non-repetitive current value of any diode as its operating value at any case because it was shown for safe band region consideration only and should only use the max. peak forward current value as operating !!.... The induction effect of an electrolytic caps. can be effecting for frequencies like MHz or very short time periods like micro-sec or nano-sec but in our design case , we are in the band of Audio Frequencies and pulse duration of ( 100 micro-sec or even more up to 1000 ) so the induction effect will not be considerable at all.... On the other hand , switching high currents at short time periods need multiple electrolytic caps.connected in parallel to reduce the heat generated by the caps. ESR and to reduce the ESR itself by equivalent cct..... and great thanks for your efforts to teach the world anyway....
This is a great opportunity for you to make your own video regarding this subject. Build your own circuit and demonstrate its operation as you stated. I will show your link at the end of my video and post it in the description box. This will get your channel going where you can add more videos with varying subjects.
