Controlling solenoids dilemma

Using Arduino Motors, Mechanics, Power and CNC
1

Hi guys.
Need your advice. I want to control about 80 24VDC 250mA solenoids at the same time. So I plan on using 74hc595 shifters, but also I would like to use LEDs for every channel as a control. I have a kind of a dilemma on how to do that.

  1. Using transistors for each channel. TIP120, or maybe some mosfet transistors ( irf530 for example ).
  2. Using optocouplers for each channel. Not sure yet what type I should use.
  3. My favorite. Using uln2803 Darlington chip. The best thing with this chip is that with just one I can operate 8 solenoids.
    What do you guys think is the best solution? Keep in mind that the financial aspect is very important for me ( besides the quality and stability ).
    Maybe you have another better idea?
2

Hello
Darlingrton can get hot at such current
Optocoupling would give You some extra isolation from inductance sparks (That can mess uC )
Mosfets are fine but be sure to use ttl level triggered

I had same problem and I decided to use relays (trigered by ULN2004 with diodes)

3

Just found out that uln2803 can give only 175mA ( or less ) when all 8 channels are turned on. So, I suppose that's out of question.
Using relays in unacceptable for me because of the price. 80 of them can get veeery expencive.
Since that I'm just the beginner, I did not quite understand what did you mean by " be sure to use ttl level triggered " . Can you please explain a bit?
Thank you. :slight_smile:

4

Y2K986:
Just found out that uln2803 can give only 175mA ( or less ) when all 8 channels are turned on. So, I suppose that's out of question.
Using relays in unacceptable for me because of the price. 80 of them can get veeery expencive.
Since that I'm just the beginner, I did not quite understand what did you mean by " be sure to use ttl level triggered " . Can you please explain a bit?
Thank you. :slight_smile:

Standard MOSFET transistors require a full +10vdc applied to their gate terminal to fully turn on. Logic level MOSFET transistors will fully turn on with the +5vdc that arduino output pins can provide, so they are the best choice to use in your type application.

5

Cheapest solution might be bipolar switching transistors - plenty out there that can handle 0.25A, I've used ZTX450's quite a lot - nice and small, 1A continuous, will happily drive 0.25A at 20mA base current.

Also I think there are some ULN2803-alikes that use MOSFET output stage and can handle higher currents, but I might be wrong about that.