I am trying to drive the Firgelli PQ-12f linear actuator from a PIC output.
The output of the PIC is 5V as is the input required for the PQ-12f. However, simply connecting them does not work. I'm guessing that the power supplied by the PIC is not high enough (The actuator is supposed to draw about 250 mA).

I'm a little hazy on op-amp setups. I need to keep the output voltage at 5v but increase the current (right now it is drawing around 50 mA, according to my lab partner).

Anyone know what to do?

 

you could use a transistor, connect it to the 5V source, the signal from the pic and the input to the actuator, just make sure you choose a transistor that can provide at least 250mA, the BC547s I have can do 500mA

 

Use an N channel logic level friendly mosfet. almost 0 heat and the circuit is really simple.

 

I forgot to mention that I need to drive the actuator forwards and backwards, meaning that the PIC is supplying +5 and -5 (and also 0 when not moving...). Basically the 2 output pins are set to (HIGH, LOW) and (LOW,HIGH) for the different directions.

Now how do I amplify the current for both directions?

Please be as specific as possible, thank you.

 

You could use a device known as an H bridge to get the directional change or if the operating fwd/rev are at a low rate a couple of transistor/relay circuits.

You cannot get -Vout from a PIC.

__________________
Eric " Good enough is Perfect "
I will NOT answer PM's requesting technical help, please use the Forum
PIC tutorials: Nigel's www.winpicprog.co.uk/ Bill's: www.blueroomelectronics.com/

 

I'm thinking about doing this:

taking two op amps, connecting the output of each one to its own inverting input, connecting the two PIC outputs to the two non-inverting inputs, and sticking in the actuator between the two outputs of the op amps.

will that give me a greater current due to the output stage of the amplifier?

 

I looked at the data sheet and the device takes around 250mA maximum and you need to reverse it (forget the +5, -5, etc). What you need to use was mentioned previously and is called an H-bridge. The truth table is as shown here:

Actuator pin is Pn where n is 2 or 3., V represents your drive voltage. 0 is ground.

P2=V, P3=0 Actuator goes one direction
P2=0, P3=V Actuator goes other direction

Since this motor is kind of small, you could also use a Dual MOSFET driver. They are available in DIP packages and are easy to interface to a micro. This is probably less total parts than the h-bridge.

 

if you have a spare servo you can rip out the guts and use the board for it. that way it's one i/o pin and you have allot of control over it in regards to speed and such