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[on:]

I am looking for a cheap way to control a linear actuator as well as a few other motor. I Think this would work. https://www.sparkfun.com/products/11593
I noticed though it max current of 4 amps and my linear actuator is rated for 7 amps stall. since this board has 5 channels can I connect 2 channels together to get more current?  also would the boards current sensor still work?

[Reply #1 on:]

It would be better to use a power transistor or MOSFET to do the job. They can handle 7 amps easily with a proper heat sink.

[Reply #2 on:]

yeah but I need forward and reverse of the actuator.

[Reply #3 on:]

lots of h-bridge options on ebay.

http://www.ebay.com/sch/i.html?_sop=15&_sacat=0&_from=R40&_nkw=h-bridge&rt=nc&LH_BIN=1

[Reply #4 on:]

If you need a high-current h-bridge controller for a linear actuator, honestly a simple relay-based controller might be your best bet. There are many linear actuators that operate fast enough (that is, extension/retraction rates) to have to bother with PWM or other speed control of the motor. You just need the ability to switch control of the direction of the motor. A pair of simple SPDT relays would do this trick easily, and on ebay you can find a ton of vendors out of China selling such boards (dual-relay control PCBs) for under $5.00 USD each. You could also opt to build such a board (depending on what you have for parts and whether your investment of time will be worth it).

For your other motors, though - if they aren't linear actuators, you should ask yourself whether you will need or want speed control for them or not (as well as how often you will switch the direction of the motor; this applies to the linear actuator as well); if you don't need speed control, and you won't be switching direction constantly and quickly, then a relay-based controller can work well (unless you can find an all-electronic solution that meets your needs otherwise).

[Reply #5 on:]

I'm keen to know what linear actuator you use please? One of these Firgelli ones, or something cheaper?

[Reply #6 on:]

I am using this linear actuator http://www.pololu.com/catalog/product/2348
I was hoping to have speed control of it, but I would probably get a relay H-bridge if it was cheaper than 15$ and was assembled.

[Reply #7 on:]

Why don't you use the controllers that Pololu themselves recommend on that link?

[Reply #8 on:]

I am using this linear actuator http://www.pololu.com/catalog/product/2348
I was hoping to have speed control of it, but I would probably get a relay H-bridge if it was cheaper than 15$ and was assembled.

From a control point of view a lot depends if you bought the model with an internal feedback position pot so your control system will know what position the actuator is at any specific time. If you lack that feedback option there is little point in driving the actuator at a variable speed in my opinion as you would have no idea where the actuator is in it's travel range and you would just be relying on the built in limit switches on the actuator to stop when travel reaches either end position. If you lack the feedback pot you are probably better off just driving the actuator with a DPDT relay that just applies voltage to the actuator at either polarity to travel the direction you wish and the actuator will stop via it's limit switches when it reaches an end point.

 So the question that you need to ask is does your application require closed loop control or is simple open loop control good enough?


Lefty

[Reply #9 on:]

The Firgelli -R range has built in servos for positioning....

[Reply #10 on:]

well I am going to have to get this for other motors https://www.sparkfun.com/products/11593
will I be able to combine 2 channels to get the current I need?