# Simple DPDT circuit

Discussion in 'Electronics Homework Help' started by infernowheels, Jul 20, 2015.

1. ### infernowheels

17
0
Jan 3, 2015
Hey guys, we were asked to create an incomplete schematic diagram(no source and no ground) utilizing DPDT switches that simply connect inputs(Common) to a certain output.

First problem:
Position 1 of the switch:
Input A is connected to Output C while Input B will be connected to Output D.
Position 2 of the switch:
Input A will now be connected to Output D while Input B will be connected to Output C.

Second problem:
Position 1 of the switch:
Two LEDs in Series will activate.
Position 2 of the switch:
The Two LEDs will still activate but now in Parallel.

Any help, even a hint would greatly appreciated!

2. ### Harald KappModeratorModerator

11,799
2,749
Nov 17, 2011
Problem 1 hint:
1. 1 relay DPDT will be required (alternatively 2 relays SPDT)
2. Inputs A and B are connected to the common pin of a switch group (3 pins per group: common,. n.o., n.c.)

Problem 2 hint:

Again 1 DPDT relay is required.
1. LED 1 is connected e.g. anode to V+, cathode to common of first switch group
2. LED 2 is connected e.g. cathode to V-, anode to e.g. n.c. contact of second switch group
From there on you should be able to find the solutions by yourself. Show us your schematics to verify them.

3. ### infernowheels

17
0
Jan 3, 2015
Refer to attached file. Not quite confident with my work though :<

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4. ### Harald KappModeratorModerator

11,799
2,749
Nov 17, 2011
You should be, though.
Perfect - with a grain of salt: The symbol with the three separate dashes used in circuit 2 is (almost) never used for V+, only for ground, earth and such. As V+ is not often ground, avoid using this symbol.
In every case avoid using this same the same symbol twice for different voltages (here: GND and V+).

By the way (unrelated to the task you have solved well): LEDs should never be connected to a voltage source without some means of current limiting, e.g. a resistor.Want to know more? Read our ressource.

Martaine2005 and infernowheels like this.
5. ### infernowheels

17
0
Jan 3, 2015
Many thanks kind sir!