Fault in 1 of 3 PICSteps... Suggestions ?

[Agro]

Hi all,

I have made three picsteps for my project connected via the Pmino 4 axis BOB. All three boards have been tested independantly using the same stepper motor and the same port and cabling from the BOB.

2 of the steppers work as expected with the stepper moving in both directions, albiet not as cleanly and quickly as I would like (probably a software issue).

on 1 of the boards it seems only one of the stepper connection blocks is active, only one coil is 'actuating'. Putting a multi meter across the terminal blocks also supports this observation.

I have checked the board and all components, links and connections are as expected. On a just in case basis I have checked for breaks in the tracking and have resoldered all of the joints which has not changed the behaviour of the circuit.

I suspect I have a dud LMD, however given the expense of this component I would like to make sure.

I have access to multimeters, a lab power supply, and can fasion a logic probe if required. I do not have a CRO or similar so this is not an option.

One thought is to de-solder and swap the LMD's tonight to see if the fault moves accordingly. Other than that I'm at a loss to explain this one.

Any suggestions ?

Cheers
Jason.

[fkaCarel]

Connect a working board and the not working board and compare them with your multimeter.

Carel

[pminmo]

Make your measurements on the pin of the lmd not the circuit land.
A few things to check. Is either of the outputs presenting a steady state voltage that is near you power supply voltage or 0 volts or do you measure some odd voltage?

Do you have 5V at pin 14?

If you had access to a scope I would suggest checking pin 3 to see if your getting some indication the timing circuits working.

What is the voltage on Pin 9 of the LMD?

[Agro]

> A few things to check. Is either of the outputs presenting a steady state voltage that is > near you power supply voltage or 0 volts or do you measure some odd voltage?

One output is at supply voltage, the other is at 0v.

> Do you have 5V at pin 14?

yes on both chips.

>If you had access to a scope I would suggest checking pin 3 to see if your getting some >indication the timing circuits working.

Agreed - I used to have access to one. Not these days though.

>
>What is the voltage on Pin 9 of the LMD?

Supply voltage (25.7v).

I swapped the LMD's in the circuit and the fault moved accordingly. All input voltages match up and the signal is being received from the PIC, so it is looking like a dead LMD. I will order a replacement this week.

Cheers
Jason.