Relay Operation - Page 1
Forum section: electronics / beginners

author: J_C
author_rank: Contributor
timestamp: October 14, 2018, 08:44:01 am
content: I have a relay that Isuspecthas gone bad, but I don't understand its operation.The best I can figure is the diagram on the side corresponds to the pin position on the bottom, but if that's incorrect, can anyone find a datasheet for this or explain how pin position is determined? I looked on alldatasheet.com and te.com but didn't find it.I know pins 1 and 4 on the left as pictured, drive a 24VAC coil but what I'm not clear about is how pins 10, 6, 7, and 9 function.This relay powers a 120VAC motor and tracing the circuit this questionable relay is in, the pin in the bottom right corner of the picture below (pin 7?) is AC hot in, and the far right middle pin (6?) needs to be AC hot out when the relay is energized, in order to power the motor.Does this make any sense? If I had no idea of the circuit this was in, just looking at the relay I would have guessed that the relay energizes pin 6 which is normally open, to close circuit to pin 9 when energized and had no connections to pins 10 and 7.?

author: SeanB
author_rank: Super Contributor
timestamp: October 14, 2018, 09:04:40 am
content: Pins 10,9 and 6,7 are each a single normally open contact. The coils on pins 1,4 are a set reset coil, as this is a latching relay, and does not need coil power to hold the contacts in the closed position. The contacts on pins 10.9 are electrically isolated from pins 6,7 and the contacts are rated for use on DC at up to 7,5A carrying or making current, and will safely break up to a supply voltage of 28VDC. On AC use they will carry or make 7,5A of load up to 120VAC supply voltage.

author: J_C
author_rank: Contributor
timestamp: October 14, 2018, 09:43:12 am
content: Thanks SeanB but I'm not sure if I'm understanding.Does this mean that if it is given a 24VAC to the coil it toggles between which pair are closed and which are open circuit, that one pair will always be closed circuit and the other pair always open?If that is true, does it remain true until the power to the coil is removed and applied again?Is it possible this relay has failed in every way? I have removed it from its circuit board, and am applying momentary 12VDC and hear it click, but it is not making any contact between any two pins afterwards. I tried applying 12VDC again to toggle it and again no contact between any two pins. I tried reversing the polarity of the 12VDC and the click sound is louder, but no contact between any two and again no contact between any two breaking and making the coil contact again.Unfortunately this relay is sealed up like a drum with epoxy on the bottom so I don't think I can non-destructively pop it open.What kind of test can I do to it to determine if it's faulty?I would have thought that if the contacts were fouled it would first (by a long shot) have been the contacts carrying the motor load (6 & 7) not the other two (9 & 10) yet I can't get any continuity reading between 9 & 10 in any test I've tried so far, and of course not 6 & 7 either which are the two that are needed.

author: PA0PBZ
author_rank: Super Contributor
timestamp: October 14, 2018, 09:56:19 am
content: Quote from: J_C on October 14, 2018, 08:44:01 amhttps://datasheet.octopart.com/R10-R0105-2-Potter-%26-Brumfield-datasheet-27866589.pdf

author: Benta
author_rank: Super Contributor
timestamp: October 14, 2018, 10:52:57 am
content: According to the datasheet, it is NOT a latching relay. It's a standard relay with 24 VAC coil. If it doesn't 'click' with 24 VAC on pins 1 and 4, it's indeed defective.

author: J_C
author_rank: Contributor
timestamp: October 14, 2018, 11:09:16 am
content: Hi Benta. It does click.I just tested as a standard non-latching relay, and that does make pin 9 contact 10, only as long as the coil is energized, but neither in this state or coil off, nor on again, do I ever get pin 6 contact with 7 which is essential for the circuit to work.I found a seller on ebay and only that one, looks like I'll have to put a NOS replacement in and if it works I'll tear open this old one destructively to see if the contacts are fouled or something.

author: PA0PBZ
author_rank: Super Contributor
timestamp: October 14, 2018, 12:14:10 pm
content: With 2 wires you can use pin 9 and 10, just put them parallel to 6 and 7.

author: J_C
author_rank: Contributor
timestamp: October 14, 2018, 10:11:34 pm
content: Pins 9 and 10 can't be parallel, are used for some other subcircuit.Here is the board I took this off of last night to retest it, still no conduction between relay pins 6 and 7 in any case, and pins 9 and 10 go off to a pressure sensor switch and somewhere else, one or two additional circuit boards from the 7 contact edge of the PCB, while the 2 contact edge goes to the motor.With luck I have isolated the fault to this  relay without having to try to reverse engineer it any further than this. The dark marks in the top side of the following pic are not burn marks, just shadows.