Arduino Forum

Using Arduino => General Electronics => Topic started by: hanyc93 on Jan 02, 2013, 11:58 am

Title: High Voltage
Post by: hanyc93 on Jan 02, 2013, 11:58 am
Hi,
Do anyone know how to use arduino to turn on a 120 V fan?

Thanks!
Title: Re: High Voltage
Post by: cjdelphi on Jan 02, 2013, 12:37 pm
I'd use a relay.. any old relay, or buy a breakout board with a relay on (comes with optoisolaters/diodes)
Title: Re: High Voltage
Post by: Grumpy_Mike on Jan 02, 2013, 12:40 pm
Or use a solid state relay, they are called SSR
Title: Re: High Voltage
Post by: hanyc93 on Jan 02, 2013, 12:42 pm
Thank you!
Title: Re: High Voltage
Post by: rvasque on Jan 02, 2013, 05:25 pm
If it's a DC motor, you can use an SCR (Silicon Controlled Rectifier).
If it's an AC motor, you can use a TRIAC. 

You can also use mechanical relays, or solid state relays, or Mosfets.

Since it's line voltage, might also help to have some physical isolation between your low voltage electronics and the high voltage section (for added safety). You can use "optical" equipped mosfets, etc...  basically, your low voltage electronics turns on a small LED (inside the mosfet), and the light emitted is detected, which then switches/turns on the high voltage side of the Mosfet (everything happening internally).
Title: Re: High Voltage
Post by: JimboZA on Jan 02, 2013, 05:35 pm
Adafruit has this (http://adafruit.com/products/268).

Disclaimer... it says something about derating when the load isn't resistive and I think a motor is inductive?
Title: Re: High Voltage
Post by: rvasque on Jan 02, 2013, 05:41 pm
Thanks for the link. That is pretty good pre-packaged solution.

For motors, use 20% of rated... so 15A x .2 = 3Amp max.
Title: Re: High Voltage
Post by: retrolefty on Jan 02, 2013, 06:56 pm
Quote
If it's a DC motor, you can use an SCR (Silicon Controlled Rectifier).


That is not true, a SCR will not control a DC motor as once you trigger the SCR on the only way to turn it off is to remove power from the motor circuit.

Lefty

Title: Re: High Voltage
Post by: rvasque on Jan 02, 2013, 07:01 pm

Quote
If it's a DC motor, you can use an SCR (Silicon Controlled Rectifier).


That is not true, a SCR will not control a DC motor as once you trigger the SCR on the only way to turn it off is to remove power from the motor circuit.

Lefty




You're right about the SCR. I was just thinking of turning it ON. 

Title: Re: High Voltage
Post by: Docedison on Jan 02, 2013, 07:11 pm
No... Not Quite... @Lefty What about commutation with an inductive load?  <BFG>

Bob