PWM Driver not working Hi, i just finished setting up the PWM driver and I hooked it up to the arduino and to the power. the power LED comes on. I uploaded the following firmware onto the arduino: [www.reprap.org] but after it finished uploading the board does not respond. symptoms: -the solarbotics motor I hooked up does not move. -the LEDs do not light up (except the power LED}) -I can tell the Arduino is running code successfully since it does print to the terminal window. I checked the diodes, the LED's the power and input connections and the screw terminals. any idea how to troubleshoot this? -Leav https://reprap.org/forum/read.php?13,18291,18291#msg-18291 Mon, 15 Jun 2026 13:24:37 -0400 Phorum 5.2.23 https://reprap.org/forum/read.php?13,18291,18345#msg-18345 Re: PWM Driver not working https://reprap.org/forum/read.php?13,18291,18345#msg-18345
By hot, I mean you would have to get the inside of the transistor more than 150C to damage it.]]> nophead Controllers Sat, 08 Nov 2008 07:51:39 -0500 https://reprap.org/forum/read.php?13,18291,18344#msg-18344 Re: PWM Driver not working https://reprap.org/forum/read.php?13,18291,18344#msg-18344

Higher voltage means that they can handle it higher, not that they need it higher, right?

Since I already have the TIP122s I think i'll solder them in, and save the TIP120s for backup, especially since they got very hot when I tried to remove them. I touched them and didn't get burnt but my finger was sensitive for a couple of hours.

Thanks again!

-Leav]]> Leav Controllers Sat, 08 Nov 2008 07:25:38 -0500 https://reprap.org/forum/read.php?13,18291,18342#msg-18342 Re: PWM Driver not working https://reprap.org/forum/read.php?13,18291,18342#msg-18342 Yes TIP122 just seems to be a higher voltage version of TIP120, everything else looks the same.

The easiest way to test a transistor is with a multimeter that has a transistor test function. A simple transistor can be tested with an ohmmeter but a Darlington is actually two transistors, a diode and two resistors, so it is a bit more complicated to test. I suggest you try one by soldering it in and if it works solder the other two.

Swapping the base and emitter in that circuit will not have damaged them. As long as you did not get them too hot removing them they should still work.]]> nophead Controllers Sat, 08 Nov 2008 05:36:30 -0500 https://reprap.org/forum/read.php?13,18291,18328#msg-18328 Re: PWM Driver not working https://reprap.org/forum/read.php?13,18291,18328#msg-18328 Lampbus Controllers Fri, 07 Nov 2008 16:47:44 -0500 https://reprap.org/forum/read.php?13,18291,18320#msg-18320 Re: PWM Driver not working https://reprap.org/forum/read.php?13,18291,18320#msg-18320
I went out and bought a solder sucker like you suggested and managed to get them out! :)-D

Since it was so hard getting them out, and I have reason to believe I fried them (connecting backwards and also shorting the tabs), I got new transistors to solder in instead.

just a quick question: the store only had TIP122 (instead of the current TIP120), they seem to be a drop in replacement with better performance, but I am not sure.

Spec sheet: [www.fairchildsemi.com]

could someone confirm this?
(alternatively, is there a simple way to test a transistor?)

Thanks!
-Leav]]> Leav Controllers Fri, 07 Nov 2008 12:52:44 -0500 https://reprap.org/forum/read.php?13,18291,18310#msg-18310 Re: PWM Driver not working https://reprap.org/forum/read.php?13,18291,18310#msg-18310
However there are some devices, including Darlingtons, that do have electrically isolated tabs. I expect it compromises the thermal performance, but in the case of a print head driver, with a lot of transistors that need heat sinking, then you would get a big cost saving sharing a heatsink without the need for insulation washers and the associated assembly time. Also the lack of external isolation would more than compensate for the extra thermal resistance of the internal isolation.]]> nophead Controllers Fri, 07 Nov 2008 07:43:20 -0500 https://reprap.org/forum/read.php?13,18291,18309#msg-18309 Re: PWM Driver not working https://reprap.org/forum/read.php?13,18291,18309#msg-18309
Quote

The tab of the transistor is connected to the middle pin which is the collector
Uuups that's true unfortunately
And now I'm confused.. is that for all to220 , because I ripped apart some old thermoprinter where all TOcased transistors where cooled by ONE large aluminum part which holds the mechanics.

Anyway.. sorry leav, my fault.

'sid]]> sid Controllers Fri, 07 Nov 2008 07:11:52 -0500 https://reprap.org/forum/read.php?13,18291,18305#msg-18305 Re: PWM Driver not working https://reprap.org/forum/read.php?13,18291,18305#msg-18305
You can get heatsink mounting kits which consist of a mica or plastic washer to insulate the tab and a plastic tube with a flange to insulate the screw. You could get by with two, leaving the heatsink connected to one transistor.

To remove the transistors without damaging them, the easiest way is to use a solder sucker to remove almost all the solder. You can then waggle each pin individually to break it free from the pad and then the transistor will fall out.

If you don't have a solder sucker you can try to place the soldering iron across all three pads and pull the transistor with pliers.]]> nophead Controllers Fri, 07 Nov 2008 03:44:41 -0500 https://reprap.org/forum/read.php?13,18291,18299#msg-18299 Re: PWM Driver not working https://reprap.org/forum/read.php?13,18291,18299#msg-18299
relax, heat your soldering iron, take a deep breath... try again. one pin after another and make use of the desoldering pump you kept handy ;)

'sid]]> sid Controllers Thu, 06 Nov 2008 22:32:28 -0500 https://reprap.org/forum/read.php?13,18291,18298#msg-18298 Re: PWM Driver not working https://reprap.org/forum/read.php?13,18291,18298#msg-18298
4am + soldering = flipped transistors :)

-Leav

p.s.
why are they impossible to get out??!??! :X:X *head/desk*]]> Leav Controllers Thu, 06 Nov 2008 22:07:52 -0500 https://reprap.org/forum/read.php?13,18291,18295#msg-18295 Re: PWM Driver not working https://reprap.org/forum/read.php?13,18291,18295#msg-18295 (as long as you don't hit another trace with the cooler)

To make sure you can remove the cooler for a testrun, but I think the problem is elsewhere.
maybe you should try with other pins
int pwm_a = 9;
int pwm_b = 10;
int pwm_c = 11;
or check the wiring

'sid]]> sid Controllers Thu, 06 Nov 2008 21:38:18 -0500 https://reprap.org/forum/read.php?13,18291,18292#msg-18292 Re: PWM Driver not working https://reprap.org/forum/read.php?13,18291,18292#msg-18292 Leav Controllers Thu, 06 Nov 2008 20:24:04 -0500 https://reprap.org/forum/read.php?13,18291,18291#msg-18291 PWM Driver not working https://reprap.org/forum/read.php?13,18291,18291#msg-18291 i just finished setting up the PWM driver and I hooked it up to the arduino and to the power.
the power LED comes on.

I uploaded the following firmware onto the arduino:
[www.reprap.org]

but after it finished uploading the board does not respond.
symptoms:
-the solarbotics motor I hooked up does not move.
-the LEDs do not light up (except the power LED})
-I can tell the Arduino is running code successfully since it does print to the terminal window.

I checked the diodes, the LED's the power and input connections and the screw terminals.

any idea how to troubleshoot this?
-Leav]]> Leav Controllers Thu, 06 Nov 2008 20:09:44 -0500