Please Help!!!

[pixelsnpings]

PIC12F629 Prob

Hey,

Im using the 12F629, and have a problem.

I took apart a cheep RC car and Im going to use it for the chassis for a simple robot. The Motors for the chassis use 6V power input to function.

I built 2 H-Bridges to allow the PIC to control the Motors.

The power input Im using for the PIC is 4.5V or 5V.

The PIC fails to run at all. I have manually tested the H-Bridges myself and am confident that the problem is the controller.

The PIC fails to run anything. I can get a good varification for the program after flaching the chip.

I unplug the power and then reenable the power on the robot and only once in a while will the PIC activate. Then it only works for a few moments then cuts of.

I've even replaced the batteries to ensure that Im not getting a brown out.

Can anyone shed some light on whats happening please?

 

[pixelsnpings]

Hey,

Im using the 12F629, and have a problem.

I took apart a cheep RC car and Im going to use it for the chassis for a simple robot. The Motors for the chassis use 6V power input to function.

I built 2 H-Bridges to allow the PIC to control the Motors.

The power input Im using for the PIC is 4.5V or 5V.

The PIC fails to run at all. I have manually tested the H-Bridges myself and am confident that the problem is the controller.

The PIC fails to run anything. I can get a good varification for the program after flaching the chip.

I unplug the power and then reenable the power on the robot and only once in a while will the PIC activate. Then it only works for a few moments then cuts of.

I've even replaced the batteries to ensure that Im not getting a brown out.

Can anyone shed some light on whats happening please?

 

[aussiepoof]

I unplug the power and then reenable the power on the robot and only once in a while will the PIC activate. Then it only works for a few moments then cuts of.
Can anyone shed some light on whats happening please?

Hi pixelnsprings... my guess is that you're not using a 5v regulator, or thatyou've not decoupled the power supply with appropriate/enough capacitors.

If you can attach a circuit diagram we can comment more clearly and give you some salient advice...

Paul

 

[pixelsnpings]

Actually using a 5V regulator was my first attempt. After failing with the regulator I desided to use a seporate power supply for the PIC - 5V. and 12V for the motors.

And here is the schematic Im using.

 

[pixelsnpings]

The controller fails even if I simply put an LED and resistor connected to an output. I also hooked an LED/resistor directly across the power rails to make sure I was getting a proper power connection.

 

[aussiepoof]

Actually using a 5V regulator was my first attempt. After failing with the regulator I desided to use a seporate power supply for the PIC - 5V. and 12V for the motors.

And here is the schematic Im using.

You need an "LDO" Low Dropout 5V Regulator... and run it from 7.5V batteries just to be safe (the LDO will keep working as they discharge.) That or switch to the LF version of your PIC which will run from 2.5-5.5V and use an LDO 3.3V regulator in stead of the 5V one if only to isolate it from noise from the motors. In any case you need a tantalum cap across the output of the regulator, and some .1uF caps as bypass to catch high frequency noise (and a 1uF one across the motor too.)

Now I'm not an H-bridge expert so can't comment on that with any certainty

 

[evandude]

pixelsnpings, why don't you make your own thread? it's rather rude to hijack someone else's, especially when your question is almost completely unrelated to the thread, and even more so when the original thread is still in active discussion, rather than one that's already been abandoned.

to the OP... My recommendation would be that unless cost is a real issue, it might be worth it to forget the 12F629/12F675 entirely and only get 12F683's for your 8-pin parts. They can of course do everything the lesser two could do, and only cost about 25 cents more from what I saw at digikey. Similarly, I wouldn't bother with the 16F628, instead I'd go straight to the 16F88.
It's not a bad idea to buy a FEW of the "lesser" chips for those cases where you're trying to recreate someone else's documented project in which they used one of those chips, but for your own development it makes more sense to use the better chips - and then in the event you ever want to produce your project in large quantities and use a cheaper chip to save money, it's not too hard to 'downgrade' as long as the cheaper one has the features you're making use of. Just my 2 cents worth.

 

[pixelsnpings]

I apologize for interrupting this thread. I will try the suggestions you have made. and I will also start a new thread.

 

[Nigel Goodwin]

You've either connected it wrongly, or made a mistake in your programming - I suggest you post the FULL circuit, don't leave anything out.