Automated Stage Truck

[m.smith1]

Hi,

Need a little help with a project I'm doing for uni.

I'm trying to make a programable stage truck. You basically give it a list of movements and it will carry them out on the push of a go button.

Components So Far

1x Picaxe 28 with motor driver
2x 12 V wheel chair motors + batteries
1x emergency stop button
1x go button
4x ultrasonic range sensors

I just need to check that the way I'm going about this is right.

I plan to make 4 relay circuits. these will control forwards and backwards movement on each motor. The relays will be switched directly from the outputs on the picaxe controller. The ultrasonic sensors will pause the truck if there is an obstruction in its way.

Would I be able to run the 12V motors directly off the controller board and get rid of the relays?

Cheers

Mike

 

[MORA99]

The motors probaly use a lot of current (compared to the picaxe), so relays or a good motor driver will be needed.

You (may) need a transistor (and resistor to base) from the picaxe output to the relay, since they can draw too much current, and you need the back-emf diode (See interfacing circuits manual).

Maybe during development, some system to make sure the motors dont run for more than xx secs, if the picaxe locks up ?

What do you run the picaxe off ?, it cant take 12V directly.

 

[craigcurtin]

Relay driver board

Noticed the other day on the Farnell site - they have some 4 way opto isolated DC relay boards that can be driven directly from a Picaxe. They also seemed to be ridiculously cheap at less than US $20.

You could use this directly from your Picaxe and then into the Wheelchair motors. (Check the current draw if the motors stall)

Craig

 

[andrew_qld]

The picaxe won't like 12volts anywhere near it (6volts absoloute maximum) and wheelchair motors will probably draw a few amps, whereas the picaxe can only supply 20mA (thats 1/50th of an amp). Relays would be simplest- just make sure the relay you select can handle the amount of current that the motors draw.

Futurelec have some relay boards and dedicated motor driver boards that will do the trick- I bought some of their opto isolated relay boards for another project a while ago. Have a look at http://www.futurlec.com/InterfaceBoards.shtml They also have an Australian site (my stuff arrived from Thailand though).

 

[m.smith1]

Cheers for the quick replies.

Can't seem to find the relay board on the farnell site. You got a link?

The only issue i have is being in the uk so trying to find a supplier here as i need the board asap.

Got to be finished for Wednesday. Everything is ready except for the relays. Spent the day wiring everything else up and one late night of writing the program.

Will post pics if people are interested.
Mike