Switch Delema

Switch Delema, 5 switches 2 purposes

Ok so i have 5 gauges wired with a power wire for the gauge and a seperate power wire for the light. i have 5 spst switches wired for the main power and the lights. what i want to do is have those 5 switches turn on the gauges and their lights together individually. but i want all the lights controlled by the one seperate switch, basically i need some way to do this other than 5 relays. can this be done by wiring transistors in line some how? the lights are just a single led so the power to tbe light is 12v probably about 20-30 mA how could i go about doing this? i have the 2 15 packs of transistors from radio shack, both npn and pnp. any help would be great. and if it can be done using strictly radio shack parts that would be best. i cannot order things online easily. thanks!

Hi,

you just need diodes to switch on all lights at a time.

Depending on the power the lights consume adapt the diode switching capability accordingly.

The 1N4148 used in the sample circuit can switch 100mA at 50V. The 1N4001 can switch 1A at 50V for example.

The circuit fig1 shows LED3 activated with an SPST switch. Fig2 shows all lights activated with SW6 on. This switch overrides all others.

Remark: Using the override switch the resultantant LED supply voltage drops by the forward voltage drop of the diode. For least voltage drop use a Schottky diode. (e.g. BAT49)

Boncuk

BTW, switches don't normally cause dilemmas. It's more likely the dilemma has another cause.

thanks but thats not what im trying to do. i want to control the lights individually, but only allow the light to go on when a master switch is on. only for the switches that are on.

Not a problem either.

MS is the master switch. It allows to switch (activate) S1 through S5.

Neither transistors nor diodes needed in that case.

Boncuk

Just connect a switch from the all-joined-together cathodes of the LEDs to 0v, no transistors or relays required. With the switch off, no leds will light up. Switch on will only light up selected on LEDs. Is that the function your after?

bassnut said:

Just connect a switch from the all-joined-together cathodes of the LEDs to 0v, no transistors or relays required. With the switch off, no leds will light up. Switch on will only light up selected on LEDs. Is that the function your after?

Click to expand...

Where do the anodes grab their positive voltage from?

The OPs circuit is a bit odd, but if I read it correctly, the anodes just connect (via a resistor) to the guage power lead?

the only problem witht that design boncuk is that i want to still be able to turn oin the gauges. and the leds arent directly hooked up, theres a light input wire that accepts the 12v power to light the gauges. so i need 2 still be able to turn on the gauges without the light but then when i want to turn on the light i just flip one switch and whichever gauges are on, the light comes on as well

so in the end i need 10 seperate power wires controlled individually by 5 switches with 1 other switch to turn on 5 of the circuits, but they all need to be isolated from eachother.
this is why i was thinking i could use 5 relays to control the light wires, one switch to energize all the relays and only the ones that are on will light, but i was hoping there was a simpler solution, i dont know a whole lot but from what i gather, transistors are similar to relays, hence my theory.

On the 1st original pic, there is a question mark symbol, and on the second it looks like a direct connection?. If the "lights" (LEDs?) anodes are connected to the guage power, then its a no brainer, the cathodes can be connected together through a switch to 0v. LEDs only conduct one way, so theres no back feed.

bassnut said:

On the 1st original pic, there is a question mark symbol, and on the second it looks like a direct connection?. If the "lights" (LEDs?) anodes are connected to the guage power, then its a no brainer, the cathodes can be connected together through a switch to 0v. LEDs only conduct one way, so theres no back feed.

Click to expand...

lol no the second pic shows what i was thinking would work if i put transistors all hooked up to a single switch int that spot. i dont really know how 2 use them so that was my guess at how it would look.

Okay so i figured out on my own that the transistor idea worked flawlessly, by using the proper resistance values, and this diagram, i hooked up 5 transistors, using 1 switched collector pin for all 5 and ran each power wire through the transistors, and success!!! each light and gauge can be turned on individually and all the lights can be turned on or off by 1 switch. thanks to everyone that tried 2 help.