Double Light switch for Telescope dual fan

Calibos

This is actually for a double fan to cool the mirror of a Telescope. (2 wires each fan, 4 in total) I have a battery pack for it which consists of 8 D-Cell batteries delivering 12v.

For all intents and purposes this is a double light switch question, where the live and neutral of the battery pack is the 230v, and the double fan are 2 light bulbs.

I dug a triple lightswitch out of a drawer. Middle switch is broken. I was using the switch either side. I assume this is in effect now a double light switch and that the broken middle switch does not affect the operation of the switch either side of it?

Tried a few combinations and the best I could get it was 'both fans off', 1 fan on full speed/other off, both fans on half speed. fan 2 was dependent on switch for fan 1.

What I would like is 'both fans off', 1 fan on full speed/other off and either fan on or off independent of the other fan, 2 fans on full speed

Probably making it sound more complicated than it is. Like I said its basically a light switch question. Double light switch(2 gang) and 2 room lights. How would I wire the double switch so that I can turn either light on or off independently of each other

northdublin

from the psu take a live from each wire and put one live into the com of each switch, then take the live going to the fan and put it into L1 on the switch. use a connector to join the neutrals.
so on the back of the switch one live goes into com and the continuation of that live goes into L1. this means your switching the live of each fan and the neutral is just connected straight trough.

Calibos

northdublin wrote: »

from the psu take a live from each wire and put one live into the com of each switch, then take the live going to the fan and put it into L1 on the switch. use a connector to join the neutrals.
so on the back of the switch one live goes into com and the continuation of that live goes into L1. this means your switching the live of each fan and the neutral is just connected straight trough.

First question. When I went to check which wire/terminal was connected to + - ends of batteries, I noticed that the plastic around one of the terminals had melted a bit and started to separate. Was this maybe overloading the battery with 2 fans or was this just the heat from the soldering iron when I was soldering the wire to that terminal?

Anyway, I hope the diagram above shows more clearly what I am dealing with.

Basically I want switch one to operate fan 1 and switch 2 to operate fan 2. So that fan 1 is on or off, fan 2 is on or off, both fans on, both fans off.

In one of my wiring combinations I found that when I switch the first fan on it ran at full speed but then when I switched the other fan on both fans then ran at a slower speed whereas if I just twisted the wires of both fans together and connected them directly to the battery wires without the light switch in between, they both ran full speed. I want both fans running at full speed at the same time or independently of each other.

Calibos

Well it looks like I got my answer to the first question. Its lucky I was dealing with batteries and 12v instead of mains.

Had fans disconnected but left battery brown and blue wires still connected to L1 and Com on switch 1. While posting the last post it seems all the other terminals connecting the batteries melted too with the batteries very hot and I think I even saw smoke starting!!!

Obviously it was not the soldering iron (Don't worry, this moron at least remembered to unplug that )

OK lets assume that battery pack is a bust. I have a ??ah 12v battery from an old UPS. Brown or Blue wire connected to + or - . Which? and from there onwards how do I wire it up without melting this battery too!! :eek:

I twisted the blues and browns from the fans together. Old UPS battery has a Black terminal and a red terminal. Fans only come on when I connect the blue fan wires to the red battery terminal and the brown fan wires to the Black battery terminal. The fans do not come on if I connect blue to black and brown to red. Hope that helps diagnosis and wiring plan.

Southern Dandy

Calibos wrote: »

First question. When I went to check which wire/terminal was connected to + - ends of batteries, I noticed that the plastic around one of the terminals had melted a bit and started to separate. Was this maybe overloading the battery with 2 fans or was this just the heat from the soldering iron when I was soldering the wire to that terminal?

Anyway, I hope the diagram above shows more clearly what I am dealing with.

Basically I want switch one to operate fan 1 and switch 2 to operate fan 2. So that fan 1 is on or off, fan 2 is on or off, both fans on, both fans off.

In one of my wiring combinations I found that when I switch the first fan on it ran at full speed but then when I switched the other fan on both fans then ran at a slower speed whereas if I just twisted the wires of both fans together and connected them directly to the battery wires without the light switch in between, they both ran full speed. I want both fans running at full speed at the same time or independently of each other.

Just loop the two commons that way each fan has power coming to it and put each brown wire (of the fan) into the L1 of each switch and join the neg cables with a connector, the reason the fans ran slow is while the other was running you brought another load on the battery drawing more power hence why it went slow, maybe use 2 power supplys for each fan to stop this, dont think running two fans on a single supply regardless of size would be good for the battery

Southern Dandy

Calibos wrote: »

Well it looks like I got my answer to the first question. Its lucky I was dealing with batteries and 12v instead of mains.

Had fans disconnected but left battery brown and blue wires still connected to L1 and Com on switch 1. While posting the last post it seems all the other terminals connecting the batteries melted too with the batteries very hot and I think I even saw smoke starting!!!

Obviously it was not the soldering iron (Don't worry, this moron at least remembered to unplug that )

OK lets assume that battery pack is a bust. I have a ??ah 12v battery from an old UPS. Brown or Blue wire connected to + or - . Which? and from there onwards how do I wire it up without melting this battery too!! :eek:

brown is + blue is -, you would actually be very surprised with the amount of current generated from such a small voltage i think you shorted it out keep the blue (neg) connected in a terminal you dont need to connect it in the switch

Calibos

Thought I was doing what you said but the battery was being shorted with sparks.

Lets start with the fans.

Twist the blue wire from each fan together. Do not insert this twisted pair into any part of the double light switch.

Take the brown wire from fan 1 and insert it into L1 on switch 1.

Take the brown wire from fan 2 and insert it into L1 on switch 2

To lessen confusion I found some black and red wire for the battery seeing as the battery terminals are red+ and Black-.

So I have a short lenght of yellow wire that I connect to the common terminals of switch 1 and switch 2. (Bridging the commons)

OK Where do the Red+ and Black- wires from the battery go. I tried several combinations and either the fans didn't come on no matter the switch(on/off) or else I got sparks from the battery terminals.

I take it one of the battery wires goes into one of the commons shared with a bridging yellow wire, but which terminal do I connect the other battery wire to.

Calibos

Found the problem.

There was no indication which of the wires in each fan pair was which. I wired each pair into a single spare PC hard drive molex power connector and wired 2x2 core(brown and blue) to the other half of the molex. The molex is there so one can connect and disconnect the fan cables easily when setting up and breaking down the telescope. Turns out I had wired the blues to the + pins of the molex/fans and the browns to the negatives.

So when I followed your instructions and wired all the blue(negs) together with battery cable going to the negative terminal, I was in fact connecting the +(Pos) fan cables to the -(neg) battery terminal. Not taking apart the molex again so now that I knew that in my arrangement the brown fan wires where negative I wired it thus:

2 Brown fan wires twisted together with black cable coming from the negative terminal of the battery. 2 Blue(Pos) fan wires connected to L1 and L2. Yellow bridging wire going from com to com. Red wire from battery positive terminal going to one of the coms sharing with bridging wire.

Fans now operate like I wanted, no sparks pops and crackles when I connected the circiut and the battery is not getting warm never mind melting.

Phew!!:D

Thank You so much Southern Dandy!