Help on Step Genie Circuit

Well I am attempting to use the Step Genie stepper motor controller to controll my RepStrap, but I am having issues with it. I am using the schematic on the step genie website [www.stepgenie.com] and when I test my circuit on either a breadboard or on my stripboard without the HEXFETs attached I get voltage on the appropriate pins at the appropriate times (I can only test this triggering the circuit manually not being controlled with the Arduino, I dont have an oscilliscope and I cant measure voltages changing that fast with a multimeter) but when I connect the HEXFETs either with wires running to HEXFETs on a breadboard or with the HEXFETs soldered onto the stripboard, I dont get voltage on any of the stepper motor output pins (Output A, B, C, and D onthe step genie datasheet) or on the TP1 pin which I think though not sure is just shorted to Output A (When Outpit A is high TP1 is high). I have checked the Enable pin and it is low (does active low just mean that the pin wont float low i guess?) just like the TP0 pin. It appears to me (though I probably know just enough to get my self in trouble) that the HEXFETs are pulling down the voltage on the Output pins but this doesn't sound possible and I might be wrong.

Could somebody please tell me what might be wrong with my circuit (or my HEXFETs) and how to fix it? I am happy to provide any more information if it is needed. Thanks for any help! BTW: My blog is new Check it out if your interested!

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Yes my Avatar is My RepStrap.....Isn't it pretty

For the latest Updates check my main site [www.repstrap.weebly.com] or my blog [www.pingiscoolest.blogspot.com].

hey there

looking at the diagram i think what your doing is using the common wires as a voltage source and using the FETS to turn on the ground to coils when you want them to turn on. dont think you will see much on a multimeter when you are testing this way but it should drive a stepper motor.

hope this helps

simon

The gate connection of a FET has a very high impedance so it would not be able to influence the voltage on the outputs of the Step Genie. Are you sure you have the FETs wired correctly?

You should not leave the enable pin floating, it should be tied to ground if you are not using it.

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[www.hydraraptor.blogspot.com]

Sorry I guess I wasnt clear I did not measure the voltage on from the 12 volt line to the HEXFETs I measured it from the Output Pin to the ground, is that what you meant? I thought I had the HEXFETs wired right , I guess I'll check again... anyway thanks for all the help.

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Yes my Avatar is My RepStrap.....Isn't it pretty

For the latest Updates check my main site [www.repstrap.weebly.com] or my blog [www.pingiscoolest.blogspot.com].

wow um sorry guys Im feeling pretty stupid right now. I was applying +5 volts which wasnt stepping it because the input pins float high. I now am able to step the Step Genie by appling ground to the step pin. now my problem however is that on my when I have +5 volts on the gate of the HEXFET, I still have a fairly high resistance between the drain and ground, enough that connecting the positive lead of my multimeter to +12 volts and the negative to the drain of the HEXFETs, I only get 8 volts on the readout (I know this is a very step by step recount of what I did but I couldn't think of another way to right it ). What would cause this high resistance? Is my HEXFET fried? Something else, once I attach my stepper motor I lose voltage on the output pin of the Step Genie, I wonder what could cause this?

That doesn't make sense at all. Can you post the part number of the HEXFET and a picture of how you have connected it.

Either it isn't an N-channel MOSFET, it isn't wired correctly, or it is fried.

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[www.hydraraptor.blogspot.com]

Ok here it is thanks for the help.
I am not sure exactly what part number it is I bought it from the step genie site (http://www.stepgenie.com) it is the second one the one that cost $.60 each. I have the middle pin wired to the OUTPUT Pin of the Step Genie, the pin on the left when viewed from the side with the metal plate wired to the Ground and the pin on the right when viewed from the same side wired to my stepper or in the case of testing with my multimeter the black lead. It is possible I have fried my HEXFET (I seem to be frying a lot of sensitive electronics) I will try to test that .

No you have them wired wrong. The middle pin and the tab is always the drain and should be wired to the motor.

Not sure which is source and gate from memory, what is part number on the device itself?

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[www.hydraraptor.blogspot.com]

Looks like pin 1 (on the left with the tab upwards viewed from the top face) is the gate (goes to the step genie)

pin 2 is the drain (goes to the motor)

pin 3 is the source (goes to ground)

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[www.hydraraptor.blogspot.com]

Not sure what is the part number but it says on the front of the Transistor

f1j09aa
fdl
8778

The first F is a very strange looking F, maybe a symbol of something that resembles an F.
Wow thats a pretty big mistake, don't know how I pulled that one off . A google search for those lines turned up nothing useful , Thanks for the help Nophead!

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Yes my Avatar is My RepStrap.....Isn't it pretty

For the latest Updates check my main site [www.repstrap.weebly.com] or my blog [www.pingiscoolest.blogspot.com].

IT WORKS!!!!! After many hours of rewireing and troubleshooting my stepper motor controller finnaly drives a full size stepper for the first time!!!!! Now my next problem is my powersupply is quite lacking in power (2 phases at once per stepper at 1.3 amps phase=2.6amps per stepper=7.2 amps total, my power supply maxes at 5 amps oops ), I guess I need a bigger and better power supply... anyway this is one giant leap for me and my RepStrap Thanks guys!!

Edited 2 time(s). Last edit at 04/18/2009 11:17PM by pingiscoolest.

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Yes my Avatar is My RepStrap.....Isn't it pretty

For the latest Updates check my main site [www.repstrap.weebly.com] or my blog [www.pingiscoolest.blogspot.com].

If you can add the 'enable' lines will this reduce the current draw? A RepRap rarely uses all three steppers at the same time (the z is only used for layer height), so this *might* help.

Sorry, electronics isn't my thing :-)

Well the Step Genie has an enable pin just cant figue out how I would activate it with the arduino. I am not a firmware coder so I dont know how to add this feature to the arduino firmware.

... this is a bot-worm, invading the forum , so no need to communicate with ...

Viktor

I'm surprised it got past the CAPTCHA, anyway that makes more sense LOL. Thanks

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_______________________________________________________________________________________________________

Yes my Avatar is My RepStrap.....Isn't it pretty

For the latest Updates check my main site [www.repstrap.weebly.com] or my blog [www.pingiscoolest.blogspot.com].

The enable line must be tied to ground for the StepGenie to work properly.