controller built on breadboard

Hi, all

I finished my first stepper controller board, so I figured I'd share it.
It's basically the rrrf 1.2 controller but with two L298s to provide up to 4 amps of current (although the diodes are only 3A so I don't know if they'll like that).

I wired it up using breadboard since there was no availability of PCBs from rrrf (and due to the design change).

Please please please realize that I'm a rank novice at this stuff - there may be mistakes and poor or strange design choices. I would love to hear about them and learn more.

Hope yall find this useful, the file attached is CONTROLLER1.gif

The diodes see a peak current equal to the coil current, but they are only on for part of the cycle so the average current is quite a bit lower. So you will probably get away with it.

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[www.hydraraptor.blogspot.com]

Hi there

There's nothing wrong with testing stuff on breadboard, but a couple of holes I've fallen down in the past are:
1) a loose connection can cause really weird behaviour - try wiggling things if you have trouble.

2) because the L298s operate in switching mode, they will generate some high frequency currents. You showed a 100nF and 100uF capacitor pair across the 12V rail, which is good, but I'd put a pair (100n + 100u) right up close to the power supply pins of each L298 (i.e. 4 capacitors on the 12V rail). Some circuits I've tested on breadboard have behaved very strangely because the caps were too far away from the switches.

3) your breadboard might get a bit upset if you drive 4A through it...

Good luck.

jbb

Edited 1 time(s). Last edit at 03/17/2009 09:50PM by jbb.

I usually breadboard new circuits that I haven't built before, before I move them to perfboard or PCB. I've pushed breadboards up to 6 Amps before they started melting so it should be able to take 4 Amps. I would definitely put the caps on that jbb mentions and definitely heat sink the 298s. The diodes will be fine unless your motor shorts out and it's easier/cheaper to replace the diodes than the 298.

I would also recommend moving the whole circuit to perfboard or veroboard. Point
to point wiring isn't the greatest thing in the world, but it is more stable than being on a breadboard.

Thanks for the comments!
I've implemented your suggestions and also moved everything onto a tin can and silicone caulk manhattan style setup, details once I've gotten them drawn out and such.

I cant say I've ever melted a breadboard... you should be proud Cris =-)