Which is more suitable? In my circuit, I have a PIC 12F675 acting as a 2.5hr timer(running thru delay), and when the (delay)/timer has run out, the pin GPIO2 goes low. But during the time that the pin is high(2.5hr), I have 24 vdc going to a set of batteries, thru a relay, or a transistor. No more then 2 amps.
Which would be more efficient? The relay or the transistor? You must of figured out already, that the PIC is running the relay or transistor.
I hope this is clear enough.

 

Depends entirely on what you're trying to do?, you don't give enough information!.

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Hey Nigel, think of it as the PIC gives a signal (high) to either a relay or transistor to keep a valve open. The valve is held open until the timer runs out. What I want to know is which uses the least amount of power to actuate the valve, The relay, or the transistor.
Thanks

 

For 2A you could use a TIP31A transistor. At a collector current of 2A its base current should be 200mA but it will work (not good) if the base current is only 100mA.

A 2A relay needs a coil current of about 40mA at 12V.

A Mosfet doesn't need any current to turn it on very well.

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Uncle $crooge

 

OK Audio, It's what I thought, but again just double checking to make sure.
I thought for sure a Darlington transistor would use less energy to keep the flow of current going from collector to emitter, instead of a relay mechanically latched and held that way to do the same thing.
I guess a Mosfet can also do.
Just needed to be clear on this, as relays are expensive.
Thanxs

 

Use either a darlington transistor or a logic-level Mosfet.

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Uncle $crooge

 

Ok Thanks Audioguru, I appreciate the help.

 

If you want really low power use a latching relay.

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Bill
Smart Kits build Smart People
http://www.blueroomelectronics.com

 

I see what you mean blueroom, but trying to keep cost low as possible. I will go with Darlington, and see what gives.
Thanks for input.

 

Depending on what you're switching the relay might be the cheapest option. Why does it have to be cheap? How cheap under $10?

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Bill
Smart Kits build Smart People
http://www.blueroomelectronics.com

 

Yes under $10. I checked Digikey, and cheapest was $15 from OMRON(Latch Relay).
The whole board has to be under $10. A PIC, a Darlington and a few resistors and caps, and that's it.
I should acheive that no problem with a darlington transistor.
I hate these budget projects from the company I work for.

Anyways, Thanks.

 

The IRLZ34NPBF-ND FET at DigiKey costs $2.12 CDN and will switch up to 30 Amps. It has a max RDS on of 0.06hm: at 14 Amps with a gate-source voltage of 4V. As long as you can switch the (-) side of the solenoid, this should work fine. I'm sure if you browsed DigiKey longer than I did that you could find one that would work for even cheaper. Don't forget the catch diode!

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