SPST Switch with extra pin? - Page 1
Forum section: electronics / beginners

author: made2hack
author_rank: Frequent Contributor
timestamp: May 29, 2017, 03:16:34 pm
content: Hey all,So I have this switch. The 1B pin does not seem to do anything. What I mean is that there is no continuity between it and its neighbors (on either switches). Whether the switch / switches are turned on.Continuity exists between 1 and 1A when the switch is on and no continuity when the switch is off. Is 1B just left over from designing SPDT switches and using the same case?Thanks,

author: rstofer
author_rank: Super Contributor
timestamp: May 29, 2017, 03:20:08 pm
content: Perhaps the switches are lighted, or could be in a different model using the same case?I couldn't immediately turn up a datasheet.

author: rdl
author_rank: Super Contributor
timestamp: May 29, 2017, 03:26:36 pm
content: Quote from: rstofer on May 29, 2017, 03:20:08 pmLighted is a good possibility. The transparent red plastic is often used with lighted switches. The extra connection will be for the light source. It could use either LED or a neon bulb. Both of those will measure as an open circuit.

author: made2hack
author_rank: Frequent Contributor
timestamp: May 29, 2017, 03:35:21 pm
content: Ok, so I gotta connect the Neutral Line to that?

author: Jono427
author_rank: Contributor
timestamp: May 29, 2017, 03:36:09 pm
content: Yep - agree that it's probably lighted. That specific pattern in the switch (rough squares) looks like other other lighted switches I've seen. Here is an example:http://www.allelectronics.com/item/lrs-40/120-vac-lighted-rocker-switch-spst/1.html

author: edpalmer42
author_rank: Super Contributor
timestamp: May 29, 2017, 04:27:56 pm
content: If there's a light inside, I would expect to see some info on the switch - at least voltage rating for the light.Ed

author: stj
author_rank: Super Contributor
timestamp: May 29, 2017, 04:54:22 pm
content: it sure looks like a neon rocker to me.

author: SeanB
author_rank: Super Contributor
timestamp: May 29, 2017, 05:22:36 pm
content: Generally the lighted switches have that translucent plastic, and a small neon lamp and a 100k 1/8W resistor inside to illuminate it. Non illuminated ones will have a solid non translucent case. As you get no continuity it likely is the neon version, as those are sometimes also available with a filament lamp ( 14V or 28V) as automotive parts.Easiest way is to use a spudger to carefully pop the switch lever out, and you will see inside the little neon and resistor. I have taken a few of them and done a conversion from neon to LED, using an appropriate colour 3mm LED and a current limiting resistor fitted back into the switch rocker.

author: stj
author_rank: Super Contributor
timestamp: May 29, 2017, 05:41:04 pm
content: how about a good side-on pic of both sides.then we can find a datasheet.

author: made2hack
author_rank: Frequent Contributor
timestamp: May 31, 2017, 02:23:03 pm
content: Yup, that extra pin was Neutral. It does indeed light up (halogen bulb).Thanks,

author: Zero999
author_rank: Super Contributor
timestamp: May 31, 2017, 02:38:30 pm
content: Quote from: made2hack on May 31, 2017, 02:23:03 pmDon't you mean you tested it with a halogen bulb?Mains illuminated switches don't use halogen inductor lamps. Neon is the norm but it wouldn't surprise me if LEDs are common in some modern illuminated switches.

author: stj
author_rank: Super Contributor
timestamp: May 31, 2017, 02:43:02 pm
content: yiou wont find an led in a mains switch, the resistor is too big and disipates too much heat.

author: edpalmer42
author_rank: Super Contributor
timestamp: May 31, 2017, 02:45:54 pm
content: I wouldn't expect to see a halogen bulb in a switch. Too much heat and too hard to replace. Neon is much more likely.Ed

author: Brumby
author_rank: Unknown
timestamp: May 31, 2017, 03:15:20 pm
content: Yeah ... it's not going to be a halogen globe under the rocker. If it's for mains operation, my first bet is a neon also.