transistor to solenoid question

can anybody help me figure out what transistor would work to run a 12v 19a solenoid valve from an arduino pin?

Are you SURE that's 19A? That's a lot of current for a solenoid valve.

If it truly is that kind of current, you should look into using a solid-state relay (SSR), though for those currents you're looking at ~$50 or more.

You can construct your own circuit using a couple of transistors but I'd be worried that switching that much current on and off there'd have to be pretty careful attention paid to grounding and protection.

Are you SURE it's 19A?!?!

futurlec do a 25A SSR for just under $15 SSR25A - SPST 3-32Vdc 25A Solid State Relay

Any datasheet on this device? It's a nice price, but I'd like to know what I'm getting (assuming I'm getting). Any on-resistance beyond 0.1 ohms or so and the solenoid won't be getting enough voltage to allow the full 19A.

I am glad you asked, the datasheet is here and its an AC SSR : 25A Solid State Relay Technical Data

The DC one is $5 dollars more and rated at 40A.
See SSRDC100V40A on this page: Solid State Relay

The datasheet can be found here:

Nice product.

With 0.0375 ohms of on-resistance it'll dissipate 13.5W at 19A. According to the figure on page 41 the user is going to need a heatsink and forced-air cooling (>20CFM recommended) at this kind of current.

And there's the usual "inductive loads must be diode suppressed" warning.

Yes, assuming the solenoid really does draw 19 amps continuously. I wonder what the OP is making?

it Is indeed 19 amps, according to the company rep. The solenoid in question is a 2 inch solenoid valve from jefferson valves. catalog number 1342bt16t.

"The DC one is $5 dollars more and rated at 40A.
See SSRDC100V40A on this page: Solid State Relay"

great! this sounds promising. is there any reason why i cant use a logic level fet with a low RDS? would that work?

According to the data sheet, it's 19W, not 19A. A much easier to solve problem.

Making it closer to 1 amp and not close to 20. That changes everything. lol

oh! i called the company and asked a rep who looked it up for me. guess i should have done my homework. so with 1.58 amps what kind of transistor should i use?

Sales reps are sometimes not that reliable.

I'd go with a logic level FET like you mentioned earlier.

Another option is a power transitor like the TIP102. This diagram shows how to connect a relay but the solenoid is wired up the same: Arduino Playground - HomePage