looking for transistor to work like a relay

Hi everyone,

First of all thanks for your time.

Im trying to implement a remote control for one of the appliances in my house, and have problems choosing the right electronic part.

I want to remplace the generic switch with a transistor? triac? relay? to control it using my Arduino. When I want to turn on/off the appliance y set HIGH/LOW in pin0 of arduino.

I tried using a transistor 2n2222 but the led of the appliance started to flash too quickly instead of do it slow and didn't work.

I need something that I can put the two wires of the appliance switch, and send 1 or 0 with the Arduino to start and stop it. What I can use of that purpose? Take in consideration that there is only signals on that wires, and no more than 5v.

I don't wanna use Relays, Im looking for a small footprint electronic part like transistors, but it didn't work.

Thanks for your help, and sorry for my bad english.

Can you please indicate what you're switching? 110/220V or 12V or 5V or what?

Which board? Pin 0 on an Uno (and maybe other model) is used for serial transmission; would not be my first choice as it will make debugging more difficult.

Hi sterretje, thanks for your quick reply.

Im trying to switch 5v DC. I need to close the circuir between the two wires of the old switch.

pin0 was and example. Im using pin7 on arduino uno for this test.

Right now I tried with a triac optocoupler MOC3043, and it work only to turn on the appliance, but didn't turn off. I read about it, and it looks like only works on AC.

Thanks again!

I just need like a transistor where I can put HIGH in the base and it close the circuit between the emitter and collector.

Try here, it may help.

Better to use a logic level MOSFET. Lot’s of threads here describing how to use them.

Russell.

Sorry, but it just doesn't work like that!

You must tell us what the "appliance" is, giving a circuit diagram of a reliable Web link which allows the circuit to be determined with a high degree of accuracy.

If you could work out the appropriate connections yourself, well, you wouldn't be asking here, would you?

You haven't mentioned the current - could be anything!

Hi,

Thanks everyone for your reply.

I will explain my project with a lot of details.

I have a server power supply in my home to run as 12v transformer. (HP 1300W part number# 337867-501)

To turn ON the power supply I need to do this:

Close the circuit between PSON+PSKILL to GND.

PSON and PSKILL have 3.3V to GND.

When I open the circuit, PSON+PSKILL without GND the power supply turn off.

What I want to do?

I need a way to close the circuit between PSON+PSKILL to GND using my Arduino.

What I tried?

Use a 2N2222 transistor - Result: don't did anything.
Use a Optocoupler MOC3043 - Result: Turn ON the Power Supply when HIGH form Arduino, but when I sent LOW, the power supply don't turn off.
Use a SSR Board (http://ecx.images-amazon.com/images/I/51NA39sbaTL.SY355.jpg) Result: The same as Optocoupler, Turn ON the Power Supply when HIGH form Arduino, but when I sent LOW, the power supply don't turn off.

What I can use to do this right?

Thanks for your help guys!

You could try a logic MOSFET, but, I would use a miniature reed 5 volt relay for this application.

An optocoupler might work, but with knowing the current a reed relay seems a safer choice.

A transistor can probably work if it's wired right... I assume that's a standard computer power supply, so you should be able to research how PSON and PSKILL work, and their current requirements, etc. You might need a pull-up (or pull-down) resistor, or you might need to reverse the logic, etc.

There is no electronic component/circuit that behaves exactly like an electro-mechanical relay. There are solid-state relays (or you can build a solid-state relay) but it has to be the right solid state relay for the right application. If you just need to open/close a contact and you don't know anything about the circuit, a regular electro-mechanical relay is your safest bet. (With an electro-mechanical relay you just need to guess/approximate the worst-case voltage & current.)

Use a Optocoupler MOC3043 - Result: Turn ON the Power Supply when HIGH form Arduino, but when I sent LOW, the power supply don't turn off.

That particular optocoupler has a TRIAC output, and that's EXACTLY how TRIACs (and SCRs) work... Once turned-on, they stay-on until current-flow stops. TRIACS are normally used in AC circuits because they conduct in both directions, and there is a zero-crossing twice per cycle (so the thing can turn off).

Hold on a minute here. Isn't one of those an output? If so, you really wouldn't want to ground it.

When I open the circuit, PSON+PSKILL without GND the power supply turn off.

Tie ground of arduino to ground of supply. Put resistor in series with base of NPN transistor (1k is good), emitter to ground, collector to the pin you need to drive low. Drive base high to turn on.

Or use an N-channel MOSFET.

If you need isolation (ie, you can’t connect the grounds) use an optocoupler (but with a normal output, not triac output) or relay.

Note what aarg said - computer power supplies normally only want you to manipulate one pin to turn them on.

DrAzzy:
Note what aarg said - computer power supplies normally only want you to manipulate one pin to turn them on.

This isn't a "normal" computer power supply in the sense you mean, it's a hot-pluggable server supply and according to the discussions on the RC forums, quite different from an ATX. For example, it primarily supplies 12 V at 100 A, not 3.3 V which is only the pilot.

shack18:
I want to remplace the generic switch with a transistor? triac? relay? to control it using my Arduino. When I want to turn on/off the appliance y set HIGH/LOW in pin0 of arduino.

Does this mean that you can switch your power supply on and off with one ordinary switch or push button (which one)? If so, you can stop reading this post.

shack18:
To turn ON the power supply I need to do this:
...
...
Use a Optocoupler MOC3043 - Result: Turn ON the Power Supply when HIGH form Arduino, but when I sent LOW, the power supply don't turn off.
Use a SSR Board (http://ecx.images-amazon.com/images/I/51NA39sbaTL.SY355.jpg) Result: The same as Optocoupler, Turn ON the Power Supply when HIGH form Arduino, but when I sent LOW, the power supply don't turn off.

In my opinion, this means that there is 'another way' to switch it off. Thinking of computers (in general), you switch a computer on by pushing a button for a short while; so you have a short pulse. You switch a computer off by pressing the button long (10 seconds?), so you have a long pulse. This also applies to servers as far as I know.

I don't know this is implemented in the computer's hardware/software so I don't know if the below will work.

You are able to switch it on. Have you tried to switch it off by providing a long pulse? Does the documentation says anything (can you provide a link?)?