Switching AC current

[parts-man73]

Working on a holloween project already! I have a 110 volt AC device that I would like to switch on and off at specific times. Something like 30 seconds on, 2 minutes off. I thought of course that the PICAXE would be perfect for the timing. I have a couple 08's that I ordered by accident(instead of the 08M I wanted)

Anyway...to the point. What kind of extra hardware would be needed to connect to a DC-AC solid state relay? I was thinking about using a TIP41C transistor between the PICAXE and the relay. Is this a good idea, or will it work?

I've never learned or found a resource to learn how to select the right transistor for a peticular application. Is there any suggestions on where to go to learn about that?

Thank you,
Brian

 

[whizzer]

Many of the commonly available DC-controlled Solid State Relays are designed to operate with a DC control level anywhere between 3 & 32 volts, and they have an internal current limiting scheme which limits the control current to a low value for any control voltage within this range. So theoretically, there is even no need for a current-limiting resistor!

Putting a small resistor in series with Picaxe output will do no harm though. And just make sure you do read the spec sheet first for the product you are considering -to ensure that it does actually adhere to this unofficial convention of 3 to 32 volts control.

BTW: All of the above is made possible by the fact that SSR’s generally utilise an LED on the DC input side of what is in effect an opto-coupler driving an AC switch (Triac).
And of course driving an LED is fairly straight forward

PS: Sorry about the spelling of ‘utilise’ above -our spelling here is quite British oriented!

Edited by - whizzer on 14/06/2006 16:47:11

 

[Dippy]

As there are zillions of different types, its difficult to give a definitive answer.
You don't say what make/type it is.

Here is an example of an SSR:
http://www.farnell.com/datasheets/44170.pdf

For this device the input and output spec are clearly shown. But there are gallons of all sorts on the market.

But its mega important you get the spec of the actual device YOU are using - for safety sake.
I'm not going to 'bang' on about high voltages as I'm sure you understand the potential hazards.

Have a search and have a very careful read. If you're not confident then don't do it.

 

[thelabwiz]

For $12.50US and postage, you can get a 10amp SSR that will operate on 3-32volts and requires about 6ma at 3 volts.
http://www.skycraftsurplus.com/index.asp?PageAction=VIEWPROD&ProdID=854

 

[Michael 2727]

In most cases all you will need is a single resistor only.
As has been said SSRs operate on any DC voltage
between 3V to 40V,,But you need a current limiting resistor.
They are driven internally by an LED which is
optocoupled to the internal TRIAC.
You only need to make this LED work to get power out.
The internal LED does not even have to be driven very hard
e.g. 3mA to 15mA in most cases will switch Full ON.
As long as you don't blow up the internal LED
almost anything will work.
If you do blow up the internal LED you can kiss it's A#@ good bye.
Suggest the standard 330 Ohm resistor straight from the Picaxe output.

Think of it exactly as a $40.00 LED.
If you make it light up it will work.
More than 20mA current may kill it.

Edited by - Michael 2727 on 08/07/2006 00:47:32

 

[manuka]

Never mind killing the Picaxe, as even 110V can kill you or a youthful "treater"! Use an RCD if a "wires into a pumpkin at the mailbox" sort of Halloween trick, or better now (IMHO) ultra bright battery fed 3.6V LEDs. Halloween is licence for all sorts of mayhem ...

Aside from my - ahem- near 50 years of mains work, I've a heightened awareness of mains safety due to my current south China meander. YIKES- bare head height 230V mains wiring snakes around walls everywhere. OK - I'm tall & have a 2.4m reach, but a casual reach up could be fatal... Stan

 

[Michael 2727]

Stan,
Messing with the laws of natural selection.
Opps,,!!Did I say that.

Yes Take Care whatever,,!!!
110VAC can Kill.
240VAC can Kill you even deader.

 

[alimauro]

Partsman, I too build props, but i ask why the ssr? You can get a pc relay board and have eight relays run through a uln2803A and switch up to 10 amps. If your interested let me know I have oodles of info on Hallowtronics. The 18m is perfect for the board i speak of but two 08s will work very well too and give you two threads to work with.
Is it a fogger your working with or lighting?
Edited by - alima on 08/07/2006 07:38:12

Edited by - alima on 08/07/2006 07:39:27

 

[lcampb]

ww1.microchip.com/downloads/en/AppNotes/91094A.pdf
Sensitive gate triac. Read the article on how to interface with pic.

 

[alimauro]

interesting read lantvin. Triac's look promising for A/C projects.