Driving Linear Actuator from PIC

[oferx]

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?

 

[Norlin]

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

 

[crust]

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

 

[oferx]

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.

 

[ericgibbs]

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.

 

[oferx]

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?

 

[crust]

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.

 

[mashersmasher]

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