Use SPST instead of DPDT

Thread Starter


Joined Mar 17, 2018
Hi, all.

I have one DPDT switch and three SPST switches that control different parts of a circuit as seen in the picture. Two of the SPST switches turn a buzzer on and off, and the other one turns a fan on and off. All SPST switches also turn an LED on and off to indicate the corresponding buzzer or fan is on. The DPDT switch switches a serial port (C) between RS-232 (A) and RS-485 (B), and turns on LED1 to indicate RS-232 operation mode, or LED2 to indicate RS-485 operation mode. Just to be clear, when I say "serial port", I don't mean that C is a pin of the serial port, but some circuitry that tells the serial port to operate on one mode or the other, depending on whether A is connected to C, or B is connected to C. This is the serial port of a PC104 board, and ACB is a jumper.


I want to get rid of the switches and use a DIP switch because (a) the switches take too much space on the panel, and (b) I'm not switching them that often so I'm OK with a DIP switch. The SPST switches are exactly the same as the switches on the DIP switch, but I don't know how to go about the DPDT. I'm not sure what A and B are (in terms of voltages, signal, etc)... First I thought one was 5V and the other one was 0V, so it was telling the serial port: "if 1, then RS-232; if 0, then RS-485", but I measured with the voltmeter and both were 5V. So I'm not sure how the serial port tells them apart.

I don't know if there's an easy way to do this. I've been thinking about using a 2-to-1 selector (see picture), but number 1, I was hoping there was an easier solution that doesn't involve using ICs, and number 2, I don't know exactly what the signals A and B are, so I don't know if I can make them go through the selector.


Any ideas? Thank you!


Joined Mar 14, 2008
Do they come in groups of four? I would like all of them to look the same. By the way, that's expensive!
I just did a Google search for a DPDT DIP switch and that was the first one I saw.
If you do a further search you can likely find ones that match and probably cheaper.