What If We Did This?....

[JonnyMac]

I have an idea to solve two problems that our friends occasionally face:

1) high current DC output
2) full-time PWM of a DC output

What I'm thinking I could do is create a derivative of the FC-4 that uses big ol' Darlington transistors instead of triacs.  The interface would be identical to the FC-4 in that you could turn any of the four channels on or off, or have the PWM to any level between 0% and 100%.  By using the TIP120 you could safely swtich/PWM up to three amps on each output -- this would be great for those high-current LED lamps.

Thoughts? 

[ScaryTinker]

Could it be used as a four channel DC motor controller?

[JonnyMac]

Yes, I guess it could -- but not bi-directional; since the off state of the output is open-collector there's no way to connect two output together to form a half-bridge.

[ScaryTinker]

That's really cool.   Any chance of upping the current handling capacity of one of the channels?  I looked at the wiper motor that a bunch of the suplus outfits are selling and the motor is rated at 2.5 amps - no load.   I'm guessing with a load it would exceed the 3 amp rating of the proposed board.

Here's where I'm going with this -  The board seems like a natural to control lots of different types of props driven by wiper motors.  There are lots of projects like the rocking chair, versions of FCG, thrashing body, witch caldron, MIB, that all can be wiper motor based.

One channel for the high amp motor and 3 channels for other lower current devices that support the prop.

[JonnyMac]

We're looking at the TIP120 (for all channels) which is good for 5 amps, and a socket for it that is rated for 4 -- so you'd have to go with the lower of the two ratings.  If you dedicated one of the other outputs to controlling a DPDT relay you could set the direction of motor travel before ramping it up.

[JonnyMac]

Note: I used three amps on my original spec because the socket is rated for four -- I tend to specify things very conservatively.

[gadget-evilusions]

Ok, I don't know that much about motors honestly. What kind of motors would be able to be controlled via this board? I wouldnt mind controlling the speeds on my fcg's and other things, changing the speed every so often to give differnet effects.

[JonnyMac]

Any DC motor that runs at the V+ voltage and up to about 3.5 amsp max -- I wouldn't go past that for fear of melting the sockets.

Do keep in mind that these are just ideas; I haven't yet built a board.

[gadget-evilusions]

Oh i know it's just ideas. I am trying to think of applications. I wasn't sure if it wouldn't drive certain motors (permanent magnet, shaded pole, etc...) Like I said. I am not a motor man. Give me compressed air and I am happy.