I want to trigger multiple relais over 1 digital Outpu. The current of all relays together is 1A at 5V DC. I am using an Arduino UNO. I want to make a cable tester, I was thinking of usin 3 Multiplexer (8I/O) as Outputs and 3 Multiplexer (8I/O) as Inputs. So i can test 24 wires at one time and switch the relays, which are changeover, so I can test 48 wires. I have no good idea, without making a monster circuit out of it. I would like to avoid to buy a Arduino MEGA for this.
To control relays from an Arduino, you need driver transistors. Generally easier to use relay modules if you actually need relays.
This is however not an appropriate way to increase the number of test points for a cable tester, you just need more I/O.
Three of these:
You most certainly do not need an Arduino Mega!
What kinds of tests are you running on the cables?
You might post a section of the schematic showing the actual testing and what and how you are testing. Is it continuity, capacitance, shorts, opens, etc. There are a lot of cable testers that do not have relays maybe you can be part of the silent group!
I want to test if the wires do not have short circuits and are correctly connected to the end connectors. We are using cable with a maximum of 50 wires in one.