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Topic: Running high power objects (Read 4791 times) previous topic - next topic

AKSoapy29

Hi. This is my first time experimenting with transisters, so I thought this project was pretty fun. Basically I'm controlling a dc motor (The speed,) through a transister and a pwm pin. I made a page on my website the shows you how to do it. https://sites.google.com/site/arduinosoapy29/motor-speed-controller You can also run relays to! :D
Andrew K.

cr0sh

Yeah - its always fun to see your first motor control program work (back in my day, I used an Amiga's parallel port and 68000 assembler). Something else to try is to use that 2n2222 to control a 2n3055, then use that to control a much larger motor or device (with an appropriate heatsink, of course).
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retrolefty

Nice start. You should however reconsider your choice of words 'high power' when utilizing a 2N2222A transitor.  ;D

Lefty

cr0sh

Quote
Nice start. You should however reconsider your choice of words 'high power' when utilizing a 2N2222A transitor.


I wonder if you can still find a TO-18 package 2N2222? If so, you could thermal glue a TO-18 heatsink on it, perhaps force cool it, and "overclock" that sucker...!

;D
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AKSoapy29

Maybe. But how do I get the motor to run backwards?
Andrew K.

UnaClocker

Ahh, I've been doing the same kinds of experiments myself lately. To go backwards as well as forwards, you need to build an "H-Bridge". I've built 3 or 4 different designs of H-bridges in the past week. I recommend this one:
http://www.bobblick.com/techref/projects/hbridge/hbridge.html
I've got a couple of those built now. I'd recommend building it on a breadboard first, because I know I sure had a lot of trouble keeping my Bases, Collectors, and Emitters straight on perfboard until I had the circuit built on a breadboard and could just clone it onto perfboard. That H-Bridge uses maybe $5 worth of parts, and is good to something like 8amps. Point the backs of the darlington's outward, so you can put heatsinks on them if they start to produce heat, that will allow you to get a couple more amps out of them. :)
Good luck.
Brian from Tacoma, WA
Arduino evangelist - since Dec, 2010.

Ulysses

Yes, like UnaClocker said, there are several designs for H bridges, even with electromechanical relays.

But I believe there's a simpler "H bridge" with transistors, have you tried this one UnaClocker: (on my next post)

There's no much science behind it, and it only takes 2 transistors. If you're playing with motors up to 2Amps, I would recommend both the TIP122 NPN and the TIP127 PNP.

Regards,

Ulysses L.

Ulysses

Here's the "H bridge" with only 2 transistors:


UnaClocker

That's an interesting design. Looks like you're using a pot to control the two transistors? It says Q2 is a TIP32A, what's Q1? Since it uses a pot, how would you control that with an Arduino?
I actually did use TIP122's and TIP127's because that's what I had laying around from past MegaSquirt projects.. ;) Here are a couple pictures of what I built..



Brian from Tacoma, WA
Arduino evangelist - since Dec, 2010.

cr0sh

Quote
Here's the "H bridge" with only 2 transistors:


That's not an "h-bridge" - its more like a "half h-bridge" (half-bridge?) like I was describing (note the dual-ended power-supply). Its advantage is in the fewer number of parts required. Its disadvantage is in the need for a dual-ended power supply, which can lead to issues of its own - especially if doing a battery powered design. This was a problem with the Milton Bradley Big Trak - since most of the time, the motors were being driven in the forward direction, you would end up with one half of the battery bank having a lower voltage than the other half, leading to issues of the other half trying to back-charge the lower half, causing you to have to change the batteries constantly in that toy!

;D
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retrolefty

Well it's performing the same function as a H-bridge, variable speed and bidirectional rotation of the DC motor. It's simper with fewer output transistors because it relies on utilizing a bipolar DC power supply. Also not really able to interface with an Arduino using PWM and direction control output pins without some additonal external interface circuitry.

Lefty


gardner

Quote
performing the same function as a H-bridge


No, it's not.  An H-bridge does not require a split supply.  This is a half bridge and does good stuff for sure, but an H-bridge is a very specific circuit topology that is different to what you have.

retrolefty

#12
Jan 21, 2011, 07:49 pm Last Edit: Jan 21, 2011, 08:20 pm by retrolefty Reason: 1
Quote
No, it's not.  An H-bridge does not require a split supply.  This is a half bridge and does good stuff for sure, but an H-bridge is a very specific circuit topology that is different to what you have.


I think you misread what I wrote. I didn't say it was an H-drive circuit (Reply #7), nor can it replace an H-drive circuit.

I said because this posted circuit uses a bipolar DC supply it can perform the same motor functions as a H-drive (using just two transistors), in that it can vary the speed and rotation just like an H-drive can. It's certainly dissimilar with an H-drive in that it isn't designed to be PWM modulated, nor any other digital interface to a microcontroller.

It's a cute little analog circuit but not something that is very applicable to a Arduino project. Those output transistors are going to dissapate a lot of heat working as linear amps at reduced speeds, rather then using a switching mode that H-drive circuits use.

Lefty

Valalvax

I too read his High Power as either mains or 480 voltage..

cr0sh

Quote
It's certainly dissimilar with an H-drive in that it isn't designed to be PWM modulated, nor any other digital interface to a microcontroller.


Well, that particular circuit can't, but it could be modified so it would - like I noted, a very similar circuit was used in the Milton Bradley Big Trak...
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