# Simple pwm DC controller or heater control



## xrotaryguy (Jul 26, 2007)

That's a pretty slick idea - especially if the pot can be incorporated into the stock heater controls. 

I have heard that the internal resistance of most electric heater cores will increase with temperature, so you might not have much to worry about if the IGBT fails. Well, you wouldn't want it to fail in the summer right?


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## etischer (Jun 16, 2008)

Well, I won't want it to fail in the middle of the night when Im in bed sleeping either =) I'd put a thermal fuse and a mechanical contactor in just to make sure it didn't turn on by itself. Nice minimalist design though I think. One could probably buy a 100A IGBT for around 20 bucks. 







xrotaryguy said:


> That's a pretty slick idea - especially if the pot can be incorporated into the stock heater controls.
> 
> I have heard that the internal resistance of most electric heater cores will increase with temperature, so you might not have much to worry about if the IGBT fails. Well, you wouldn't want it to fail in the summer right?


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## Jeremy (Jul 12, 2008)

It would be good if you could increase the frequency a bit. For PWM motor control to work efficiently the motor inductance needs to smooth the current pulses, resulting in much smoother, and quieter, motor operation, particularly at low speeds.

There is more on this on the 4QD web site, see here for starters: http://www.4qd.co.uk/faq/bmnc4.html#switfreq (there are other useful PWM articles on this site too).

It should be easy enough to change the base frequency for the module you've got, my guess is that simply changing the value of one capacitor is all that might be needed.

Jeremy


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## Twilly (Jan 22, 2008)

People complain about the momentary whine the curtis controller produces at 1500 hz before it ramps up to 15khz... I would assume 400hz would cause the motor to hum quite a bit... Could you use a freq multiplier to get the freq to say 4khz or higher?


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## etischer (Jun 16, 2008)

The pwm board just uses a 555 timer. Don't know how high they can go in frequency. I'm trying to build a 3 phase drive actually, but for $10 bucks I thought I'd play around with the PWM. I'll probably use this to run my heater, and not a motor though. Thanks for the tips, yea, 400 hz buzz would get annoying =)



Twilly said:


> People complain about the momentary whine the curtis controller produces at 1500 hz before it ramps up to 15khz... I would assume 400hz would cause the motor to hum quite a bit... Could you use a freq multiplier to get the freq to say 4khz or higher?


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## TheSGC (Nov 15, 2007)

I have been playing with a 555 timer for a PWM controller and they are only good up to 2 KHz. After that the square wave is too deformed to operate the motor properly. I have actually built a fully functioning controller with a 555, and I even implemented current limiting and plan on using it as a temporary controller until my programmable controller has the code ironed out.


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## Madmac (Mar 14, 2008)

Try the CMOS versions if you want higher frequency Maxim do the ICM7555.

An LC filter on the output will make it less like a broad band transmitter, or slow down the IGBT switching times at the expense of greater power dissipation. A wire wound heater element would make a good aerial. 

Madmac


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## impact1 (Jun 25, 2008)

etischer said:


> The pwm board just uses a 555 timer. Don't know how high they can go in frequency. I'm trying to build a 3 phase drive actually, but for $10 bucks I thought I'd play around with the PWM. I'll probably use this to run my heater, and not a motor though. Thanks for the tips, yea, 400 hz buzz would get annoying =)


I was thinking along the same lines, for bothe the heater control and the fan speed control in my car. I came across these kits on Ebay <http://search.ebay.com/_W0QQsassZelectro-light> 20 Amps control at 12v, full range PWM and adjustable frequency up to 120,000 Hz.

I'm also replacing the central fan with several computer style fans. Part of an effort at beter individual point control, and reduce power drain. And the old fanseemed to be dying. 


Impact1
1978 Spitfire in progress


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## Johny (Jul 21, 2008)

For a jump start on building a 3 phase controller google MC3PHAC. The Gate drivers and avoiding false firing are the difficult bit.


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## lazzer408 (May 18, 2008)

If the IC on that board is just a timer or op-amp there is at least one capacitor on it. Lower it's value to raise the freq. Or find the resistor feeding voltage to the cam and lower it's value. Or both. I bet once you start raising the freq your going to see that gate signal round off.


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## sxyrx7 (Feb 27, 2008)

whats the part number for that IGBT and whear did you get it from?


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## etischer (Jun 16, 2008)

Johny said:


> For a jump start on building a 3 phase controller google MC3PHAC. The Gate drivers and avoiding false firing are the difficult bit.


Wow, thats pretty sweet. It looks like it just does Volts/Hz mode though. Still would be fun to build a little drive and see how it all works. Thanks, that's a great find, I think I'm gonna have to buy one.


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## etischer (Jun 16, 2008)

sxyrx7 said:


> whats the part number for that IGBT and whear did you get it from?


http://www.pwrx.com/Grids.aspx?g=110&m=60

if the direct link doesn't work, just go to the site, they have the parts for sale on the website. You can also give them a call, they are pretty helpful.

-e


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## sxyrx7 (Feb 27, 2008)

thanks, i have a car sterter motor mounted on a small gokart but under testing i keep melting fet's but a IGBT might be the answer 
it runs up to 100Amp's at 12v


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## lazzer408 (May 18, 2008)

sxyrx7 said:


> thanks, i have a car sterter motor mounted on a small gokart but under testing i keep melting fet's but a IGBT might be the answer
> it runs up to 100Amp's at 12v


Mosfets are easier to drive then IGBTs.

Do you have proper gate drive? and flyback diodes?


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## kerrycar73 (Sep 4, 2012)

PWM using a 555 timer: http://play.kendincos.com/179390/Wrvfjptjntxvzvzhl-pwm-using-a-555-timer.html


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## lazzer408 (May 18, 2008)

kerrycar73 said:


> PWM using a 555 timer: http://play.kendincos.com/179390/Wrvfjptjntxvzvzhl-pwm-using-a-555-timer.html


555s make aweful PWMs. Build your own op-amp based oscillator/comparator out of an LM393.


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## Vortex (Aug 17, 2012)

I bought a pwm circuit for 10 bucks. It produces a 400hz square wave with adjustable pulse width. The 12 volt battery powers the pwm circuit.

I bought a 600A 1200V IGBT for 60 bucks. The pwm circuit turns the IGBT on and off. 

This circuit could be used to vary the power going to a big DC motor. 
The only DC motor I have is a 1/2 hp servo motor, and I suspect the 400hz would cause the motor to ring. I'll have to give it a try in the morning. 

A normal DC motor would work pretty good I bet. 

I was also thinking I could use this to run a coil for a heater, I'd just have to make sure I had a mechanical contactor. If the IGBT fails, it will fail in the on state most likely[/QUOTE]




I used a Arduino 11 which has PWM outputs to interface my motor winding PTC thermistor to the existing fuel gauge, previously driven by a NTC thermistor. It needed a MOSFET but other than that it was much easier than I expected. The code wasn't difficult, about 10 lines in all. The cost about $40.

I plan to use an identical setup to run the ceramic heater but use a pot to set the temp and maybe another PTC to close the loop and control the output air temp.


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## davemaster (May 16, 2013)

Greetings,

Can You please give us the schematic/diagram of your IGBT based circuit?

Thanks a lot


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