Does anyone know where I can get a 6 step rotary switch that can handle around 30A of 12V (this can be flexible, as long as it's close) DC? Basically, it would work like this: 1. Off 2. Device 1 turns on 3. Device 2 turns on, while keeping device 1 on 4. Device 3 turns on, while keeping devices 1-2 on 5. Device 4 turns on, while keeping devices 1-3 on 6. Device 5 turns on, while keeping devices 1-4 on As you turned the switch clockwise, power would be routed to each device next in line, as well as powering devices switched on before it. Yes, my drawing sucks...it took 20 seconds.
Haven't seen a rotary switch with 6 positions that can handel that much current, what about using a basic rotary switch with transistors to switch the current?
Are you talking 6A per device, or up to 30A per device? Either way, MOSFETs are your friend, if the devices are suitable.
You do know of course that a full 30 amps at 12V is really not good for your health? At Bell Labs I had a teammate I had to pull off a backplane where 5V at 50amps welded his wedding ring to the backplane pins and was melting the ring. Burned his finger seriously. John
Yeah, that whole 30A business was simply not a good plan from the start. I instead came across some well priced automotive relays at EPO yesterday and couldn't pass them up. They're rated at 50A each at 12V DC, and I bought 5 of them; one for each 'on' position. I also found a single pole 6 position rotary switch that I can wire the relays to, however Im running into problems here also. There are 7 connections on the switch in total. Am I wrong to assume one of the wires from the relay connects to the "common" connection, and the other wire to one of the 6 positional connections located around the switch? I also picked up around 20 IN 4003 9410 ( I forgot what they're called, but basically an electrical check-valve that permits flow going the wrong direction. Like this on a diagram: --->l---) I need these if I'm going to have the rotary switch setup to handle multiple devices. 1: 0 2: 1 3: 1+2 4: 1+2+3 5: 1+2+3+4 6: 1+2+3+4+5 That ASCII diagram sucked, please don't hate me. CPemma, each device is 6A. Oh and Jhan I'm sorry about your teammate, that must have been painful, lucky you were there. Cheesecake.
12V supply goes in to the 'common', then out from the switched poles to the appropriate relay coil through the steering diode. All relays have a common ground from their other coil terminal. You only need 5 diodes, and a better buy would be 1A Schottky types for the lower voltage drop - worst case relay will only get 9V to the coil with 1N400x, at least 10V with 1N5817 or 1N5819. Still, car relays are designed to work even with a flat battery. Code: Sw6----+--------RLY6 | V - | Sw5----+--------RLY5 | V - | Sw4----+--------RLY4 | etc Sw1----+--------RLY1 ASCII Art lesson - design in Notepad with Courier, C&P into [ code ] tags.
You rock. Thank you. I thought I'd have to use way more diodes, and have each switch get worse as I went along, but that makes 100 times more sense and is practical. How big are those 1A diodes?
CPEMMA will probably jump in on make before break switches vs break before make. What they do is keep power to the first device while adding the second. It can get interesting. The relays were a good idea, They are almost required for off-road head lights - too much current for the wires. John
Good point, if you have to use the more common break-before-make switches. With some devices (like fans) it won't matter, with others you may need a small storage capacitor on the relay coil to delay switch-off a few mS. Relays are not instant-acting, so their delay may be enough.
Hmm good stuff guys. Luckily for this particluar application I don't think I have to worry about make-before-break, but that is definitely good info. Here is basically how I have things setup so far: http://aycu01.webshots.com/image/50200/2002502888645350871_rs.jpg http://aycu09.webshots.com/image/51208/2002553317869281368_rs.jpg Since setting #1 on the rotary is off, that brings me down to only needing 4 diodes (unless I'm a total n00b and have done something extremely stupid). Also, I have all the Relay's tying in, and then running from a singular line to the "common" connection on the rotary switch. Is this a no no? Input is again greatly appreciated. I am learning so much from y'all's support and ideas on this, I don't know how to thank you enough. Yes, I just typed "y'all's" on the internet. Texas Cheesecake. P.S. Sorry for the terrible image quality. All the good uploading sites are blocked from work.
Second one you've a closed circle with no power for the relay coils; try Sorry for the terrible image quality...
Ok, that helps immensly. I was under the impression the relay coils would get power from the +12V going into the devices. Silly me. That shouldn't be too high a voltage for the switch should it? I bought it OEM at Electronics Parts Outlet, so I don't have all the technical specs I would normally like. "You mocked me once, never do it again! I DIED that day!!" Hehe, sorry. Greatest movie ever. R.O.U.S.'s Cheesecake. P.S. ^^ I don't think they exist...
Hooked up a molex to the relay, and it worked perfectly, thank you. I also got my rotary switch setup with the diodes soldered firmly in place. Pics and initial testing results coming soon.
