Electrical question

[pvr]

If a control has a 'normally open, volt free contact', and is operated by joining two wires to make a brief contact and therefore operating a motor, I assume I need a relay to make this contact?

I have a 5V source that actuates when I send some commands to it, and by this I need the wires to make a contact for as long as I open the relay. I also want to enable a timer on that relay to keep it open for say an hour or so. Does that point to a certain type of relay I need as well? Also I don't know in this type of setup if you need to have a certain relay rating or not.

 

[stupot67]

Hi PVR,
Your looking for a off delay relay, RS is your best bet, if you want I'll look you up a part No (What voltage & current are trying to switch?)
Stu.

 

[pvr]

Hi Stu - my understanding is that I am not switching due to the volt free bit? I am using a Raspberry Pi to switch the 5V part of a relay, but not sure what the main flow would be then current wise.

The wires are the switch wires of my electric gates (used by a wireless intercom) and I am using the Pi to do some switching with an ANPR camera so it will auto open the gates based on a pre-set list of number plates. Bit of a play so if I invite someone, I can just put the numberplate in the system and the gates will auto open on arrival.

Nerdie - yes, but I have a few days off at Christmas

 

[pvr]

Wonder if this would be the one:

http://www.ebay.co.uk/itm/New-5V-1-Channel-Relay-Module-with-Optocoupler-H-L-High-Level-Triger-for-Arduino-/141367934261?pt=UK_BOI_Electrical_Components_Supplies_ET&hash=item20ea2f7d35

 

[stupot67]

Hi,

That Interface relay (E-Bay Link), should be fine, as your using a Raspberry Pi you wont be needing a timer relay ('I'm assuming you will write a line of code in the Pi to take care of the off delay requirement) - 10A@240VAC will be plenty to interface with your gate control. You will need to take a +5V feed to the common of the Pi's output and then connect the output (Pi) to the interface relay and link up the 0V's (Pi & Interface relay).
Stu.

 

[pvr]

Thanks Stu, yes - I am a software man so am happy to do all the controls from that side but the switching I wanted to cross reference to someone who would know what they are talking about instead of me not being 100% sure what the "volt free" bit implied with regards to the main current.

 

[stupot67]

Hi,

"Volt free contact" is exactly what you've probably assumed it is, a switch or in this case a transistor that has no internal supply connected to it (You need to apply an external supply)

All the best.

Stu.