wiring both a dimmer switch and a three prong rocker switch to a DC bulkhead - Page 1
Forum section: electronics / beginners

author: tbarklay
author_rank: Newbie
timestamp: July 27, 2020, 02:23:45 am
content: Hello,I'm making a hot wire foam cutter with some nichrome and just need some help with some of the wiring. I've got a three prong rocker switch and a 12v 8a dimmer switch that I want to wire to a 2.1mm DC bulkhead. I've attached my diagram, but I'm not sure what to do with the negative input from the dimmer. Do I ground it on the same negative terminal on the switch as the DC?Thanks for your help!

author: ledtester
author_rank: Super Contributor
timestamp: July 27, 2020, 02:45:00 am
content: Don't connect the negative of the DC jack to the switch.Just connect your free black wire to the negative end of the DC jack.If both the positive and negative of the DC jack is connected to the switch you could short-out the power supply.

author: rantwhy
author_rank: Contributor
timestamp: July 27, 2020, 02:50:23 am
content: Hope this helps.CCF07262020.pdf(233.65 kB - downloaded 77 times.)

author: rmel
author_rank: Regular Contributor
timestamp: July 27, 2020, 03:11:00 am
content: Quote from: tbarklay on July 27, 2020, 02:23:45 amAs ledtester said, if you connect the black wire and red wires together at the "in" terminal of the dimmer, you'll short out the power supply. The dimmer should be in series with your load, so the black lines should not connect to it at all to the dimmer. I modified your diagram to what I think you should do. Use the green line instead of your original black line.

author: james_s
author_rank: Super Contributor
timestamp: July 27, 2020, 04:03:13 am
content: Is this an illuminated single throw rocker switch, or a non-illuminated double throw switch?

author: tbarklay
author_rank: Newbie
timestamp: July 27, 2020, 05:15:29 am
content: It's illuminated.

author: james_s
author_rank: Super Contributor
timestamp: July 27, 2020, 05:23:51 am
content: Ok then the switch looks ok, although I can't say for sure without seeing the wiring diagram or datasheet for it. You need to connect that loose black wire with the other black between the DC jack and the switch.I believe the other posters are confusing this DC dimmer with a standard AC dimmer switch that only has two terminals. Your drawing shows a device with 4 terminals, + and - inputs and outputs, that part of the wiring is correct.

author: eblc1388
author_rank: Frequent Contributor
timestamp: July 27, 2020, 05:49:38 am
content: Check the current rating of the DC jack/socket.One or two amperes is OK but I doubt that it can carry 3A or more without heating up.

author: tbarklay
author_rank: Newbie
timestamp: July 27, 2020, 06:50:16 am
content: like this?here's the info for the switch:https://www.jaycar.com.au/2-1mm-bulkhead-male-dc-power-connector/p/PS0522

author: mikerj
author_rank: Super Contributor
timestamp: July 27, 2020, 10:24:26 am
content: Quote from: tbarklay on July 27, 2020, 06:50:16 amThat link is for the power connector, not the switch. Your diagram is more or less correct, but fails to identify the pins of the switch. If you wire it incorrectly you could short out the supply, or the switch may illuminate whenever input power is present, irrespective of switch position.

author: tbarklay
author_rank: Newbie
timestamp: July 27, 2020, 11:26:52 am
content: Thanks.Sorry for the link - here's the proper one:https://www.jaycar.com.au/spst-medium-illuminated-rocker/p/SK0978so the switch is 1(pwr), 2(acc) 3(grnd). positive DC to 1, negative DC to 3 and 2 goes to positive input on the dimmer.here's an updated diagram.

author: james_s
author_rank: Super Contributor
timestamp: July 27, 2020, 04:58:27 pm
content: That switch is illuminated by a neon glow lamp with a resistor sized for 240VAC so it doesn't matter how you wire it, it's not going to light up if you're using 12VDC.

author: tbarklay
author_rank: Newbie
timestamp: July 27, 2020, 10:45:25 pm
content: oh, I missed that. Thanks.So if i'm not illuminating the switch, negetive DC goes straight to negative dimmer input. Adjusted diagram attached. Thanks everyone for your help!

author: Syntax Error
author_rank: Frequent Contributor
timestamp: July 27, 2020, 11:48:14 pm
content: Just a general safety point. Nichrome wire when heated expands a lot and sags, so be sure you have plenty of tensioning otherwise cutting a straight line will be impossible. It goes without saying, never touch the hot wire as goes through your skin as easily as it goes through foam. Even if the wire looks cold! And please don't breath in those white fumes, as you don't want to be foaming at the mouth

author: rmel
author_rank: Regular Contributor
timestamp: July 28, 2020, 06:37:06 am
content: Quote from: james_s on July 27, 2020, 05:23:51 amYes, I did make that mistake. Sorry to OP. I'll be more careful next time.