# Relay ?

Discussion in 'General Electronics Chat' started by Mathematics!, May 28, 2009.

1. ### Mathematics! Thread Starter Senior Member

Jul 21, 2008
1,022
4
I have a relay that I want to use to control a house switch
(120 volt AC)

The part is radioshack 275-217 DPDT Plug-In Relay.
characterisitics are
Excepted Life: 100,000 operations (min.) at rated load
Absolute maximum ratings
Ambient temp -40 to +158F
Continuous coil voltage: 132VAC
Power consumption: 1.10VA max

Electrical characteristics
Rate voltage: 110/120VAC
Coil resistance: 4.430 ohms max.
Pull-in voltage: 9.6VAC max.
Dropout voltage: 36VAC min.
Nominal coil current: 8.4/9.2mA
Contact rating: 10A at 110VAC or 24VDC
Maximum operating voltage: 250VAC /125VDC

Would this be Ok to use and if so is pin 7 and 8 on the relay where I put the 5 volts or greater to control the switch located at pin 5 and pin 6?

The reason why I ask this is I used a simple 9 volt battery on pin 7 and pin 8 to see if the contact inside the relay would move to the other direction but it didn't. 9volts is definitely > 5 volts?

Is their any specific direction on which the current should flow into the coil? Or can it go either way to get the same effected.

2. ### Audioguru New Member

Dec 20, 2007
9,411
896
Don't use a relay from RadioShack because their instructions are completely wrong.
The coil needs 132VAC?
But the coil is only 4.5 ohms?
Then the coil draws 29.3A and uses 3,868VA?

I don't think a 9V battery has 132VAC to make the relay work.

May 28, 2009
474
29
Make sure when you select your relay, take into consideration the current draw of the device you will be powering through it. Always select a relay with a higher load capability than you think you'll need.

4. ### Mathematics! Thread Starter Senior Member

Jul 21, 2008
1,022
4
Continuous coil voltage: 132VAC
Power consumption: 1.10VA max

Electrical characteristics
Rate voltage: 110/120VAC
Coil resistance: 4.430 ohms max.
Pull-in voltage: 9.6VAC max.
Dropout voltage: 36VAC min.
Nominal coil current: 8.4/9.2mA
Contact rating: 10A at 110VAC or 24VDC
Maximum operating voltage: 250VAC /125VDC

From this list they have Minimum load: 100mA , 5VDC thought this was the min voltage needed to use to trigger the switch in the relay?

What I have is a avr chip with a PIR sensor. When the PIR sensor detects a change the avr chip puts 5 volts DC down a pin to trigger the relay to turn on the high power circuit.

I am curious if this relay is not the one to use for this then what is?
And what good is this relay if you need 132VAC to operate it, what application is it used for?
Thought the point of relays was to beable to switch on high voltage circuits from low voltage circuits?

5. ### beenthere Retired Moderator

Apr 20, 2004
15,815
282
The pull-in voltage (9.4 volts) is the minimum operating voltage - the coil won't pull the armature with less voltage.

The specs are very open to question. Every other relay on earth has a dropout voltage less than the pull-in. This one drops out when the voltage is 4 X the pull-in. The coil is 4.4 ohms and takes 9 ma. The problem is that with 9.4 volts through 4.4 ohms, the current will be 2 amps, not 9 ma.

I am not sure you can trust any of those specs. Radio Shack is not the most reliable of suppliers.

6. ### Mathematics! Thread Starter Senior Member

Jul 21, 2008
1,022
4
So what type of relay or electronic component can I buy to use with a 5 volt DC circuit to control a 120/240volt AC house circuit?

Can I get this from a radioshack or do I have to send away for it?

May 28, 2009
474
29
Forget Radio Shack, its little more than a cell phone store now. You may have to order one online if you don't have an alternate electronics parts supplier in your town. Try Jameco Electronics (Belmont, CA), Mouser Electronics (Mansfield, TX) or Newark Electronics (Palatine, IL). There are numerous others that you can find online. They will typically ship same day if you pay with credit card and you will get it in a day or two.

8. ### Mathematics! Thread Starter Senior Member

Jul 21, 2008
1,022
4
That's great does anybody know if their is a electronic store near or in Northampton, Massachusetts U.S.

I prefer not to order online.
But to go into the store to buy.

May 28, 2009
474
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May 28, 2009
474
29
11. ### Mathematics! Thread Starter Senior Member

Jul 21, 2008
1,022
4

I looked on their site I cann't find them selling many electronic parts.
Their products or more for electrical house and big things. I don't see any relay's?

Although this place is very convienent driving wise.

Maybe I am not searching their site correctly under products and vendors.

May 28, 2009
474
29
Call them and ask if they know of any component stores in the area. An automotive relay will work, get one from a junkyard car. Google electronic supply stores in Hartford. You will find something, I don't have the time to do your legwork for you.

13. ### Mathematics! Thread Starter Senior Member

Jul 21, 2008
1,022
4
Ok, but when you said this
I don't think that is true car relay's are for voltages of 12 or 24 volt.
But house is is rate at 120/240 VAC.

But I see your point about doing my own leg work just wondering if anybody new of a simple store in that area anyway thank you for your inputs.