Simple wiring question - Page 1
Forum section: electronics / beginners

author: edy
author_rank: Super Contributor
timestamp: May 10, 2014, 03:05:11 pm
content: Hi folks,I have a wiring question which I was hoping to solve with your help. I have attached all pertinent files. Let me explain. There are 4 pieces of equipment in a dental office utility room.... they are controlled by a remote switching panel. They are:1. Solenoid valve to control main water2 and 3. Two vacuum suction pumps (wet type)4. Air compressorCurrently it looks like the remote panel is 24v type and each button individually switches on and off the equipment. I am not sure why there are 3 wires going to the switches as I thought 2 would be enough to either show continuity or short, but I guess it works by ground in either one wire or the other through the third.If you look at the attached drawing, it is currently wired up like the image on the top. However, I need to make sure the water is on for the vacuum to be turned on. So I want to wire it like the diagram on the bottom.... the water switch must be on and only if it is on will the 2 vacuum buttons be allowed to work. this will prevent trying to run the vacuum pumps dry and damaging them.Never mind the crude drawing and voltage divider phenomenon going on, etc... that is the basic idea I was trying to get across. Therefore I was thinking perhaps I need a couple more relays in the circuit which would be activated by the water circuit and not interfere with the operation of the water. they would simply be switched on when the water is on and provide continuity for the vacuum switches to operate.Otherwise is there any way to do this safely by just rewiring the existing buttons so that the vacuums are in parallel and together the both of them in series with the water button like shown in my schematic? I don't think it would work as I would be tying together various pieces of equipment remote buttons.Any ideas would be appreciated.

author: edy
author_rank: Super Contributor
timestamp: May 10, 2014, 03:10:22 pm
content: I have to attach files separately as they were too big for one post...Can someone please explain what the yellow brown and orange wires are in relation to the black red and white and what kind of voltage am I expecting in these things. I assume it is DC as well.

author: edy
author_rank: Super Contributor
timestamp: May 10, 2014, 03:17:14 pm
content: The PDF file shows the schematic of the control panel. I have attached a screen capture in case you don't have Adobe PDF reader.

author: Fank1
author_rank: Regular Contributor
timestamp: May 10, 2014, 03:48:21 pm
content: It looks like you have illuminated switches, the 3rd wire is the common lead for the light.

author: edy
author_rank: Super Contributor
timestamp: May 10, 2014, 04:31:01 pm
content: I noticed the yellow lead says 24 V coming off the transformer. The orange and brown are connected together through what looks like the coil in the relay. The brown wire goes through the pushbutton "lamp" I assume by the diagram and to one side of the switch (same as with orange), but whereas the orange wire bypasses the lamp and goes right around and hooks up to the same side of the switch as the brown. The yellow wire hooks up to the other side of the switch.So I take it the lamp is rated at lower voltage and doesn't need 24 V going through it, so the brown wire powers the lamp while the orange carries the full 24 V from the yellow? Or is this just to make sure the switch still works even if the lamp is burned out if it was wired in series with the switch?I guess my confusion is also about how exactly these SWITCHES operate. They are pushbuttons that light up when pressed in. How are they constructed inside? Are there actually 2 distinct switches... one that shorts ORANGE-YELLOW and a separate one that shorts BROWN-YELLOW at the same time (allowing the lamp to turn on). Or this there just 1 switch that effectively shorts the ORANGE/BROWN junction with the yellow. Does it even make a difference? And if YELLOW is the "hot" side at 24 V, then if ORANGE/BROWN are joined to either end of the coil on the relay, they would effectively be shorted and so how could current flow through the relay and active it?When the pushbutton is pressed, it would connect the YELLOW to the ORANGE/BROWN node. That would allow current to pass through both ORANGE and BROWN wires in the circuit. The lamp would light, but since ORANGE and BROWN are on opposite ends of the relay coil, what would be the voltage difference between them and how would you get enough current to pass through the coil to activate the relay? It seems the only reason is the ORANGE line provides the least impedance path and so current would prefer travelling through the coil and ORANGE path rather than the BROWN due to the greater resistance of the lamp.Or am I completely confused?

author: G7PSK
author_rank: Super Contributor
timestamp: May 10, 2014, 04:48:51 pm
content: Those lamps are neons so will need about 90 volts to strike. The best way to connect the vacum pumps would be either a water pressure switch or another relay with its coil across the water solenoid.

author: Dinsdale
author_rank: Regular Contributor
timestamp: May 10, 2014, 05:50:14 pm
content: Looks like VACSTART ELECTRICAL BOX pin 2 is tied together to serve both Vacuum Switches. A single relay could enable both of those switches. Or replace the Water Switch with a lighted 2p2t and have the second pole enable the Vacuum Switches. I see no way to rewire the available components to get the functionality you want.You're going to have to spec. out the voltage/current requirements for any new components. I can't tell how the neon lamp power interacts with the Water Solenoid Valve connection. You need to figure that out if you replace the Water switch.Or just put a sticker on it: "Turn on Water Pump first"

author: SeanB
author_rank: Super Contributor
timestamp: May 10, 2014, 08:23:03 pm
content: Get a 24VAC relay with at least 2 NO contacts. Connect the coil to pins 3 and 4 of the water valve. Connect one of the NO contacts in series with pin 2 of the one vacuum pump switch, and the other in series with pin 2 of the other switch. That way power will only be applied when the water is turned on. 1 part which you will have to fit into the box, and it can have almost any contact rating, like 2A and work here.