I am using 4 of the spark fun 7 segment displays in series with one another using a single 12v car battery for the 12v power source. The Arduino I’m using is being powered by a 9v battery, but the LED panels/Drivers need to be grounded to the board as well as the 12v power source. I’m having an issue when the DC motor is in use where the displays are displaying strange numbers, so I’m worried about the longevity of the circuit. What protections would I be able to add to the circuit? The DC motor is in use when a 5v relay closes and grounds it.
A drawing and list of particular items (DC motor could mean a lot of things) would help us visualize what you have. It isn’t clear how your controller, motors (relays, too) and displays are connected among each other or interact to show where isolation or bonding is recommended or possible.
But, in general, you’d want some stable isolation for the controller. It’s understood that motors and relays are noisy so in addition to a clean power supply, you may need some chokes or optical isolation on control lines.
Here is a very simple image of the circuit. Unfortunately, I have searched and can’t find any data about this motor. (Haokixin “600DB - 12v Car Horn” on amazon) There is no controller for this motor, just on and off. When the horn’s fuse is removed it works flawlessly. Otherwise, I’m worried about a spike in current or something similar from the motor (horn) damaging the other electronics.
Which sparkfun 7 segment displays are you using?
Your relay needs a flyback diode on the coil or it will eventually destroy the I/O pin on your Arduino.
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Yea, either some help for the relay or a solid state stage. I’ve used Opto 22s for similar applications and they’re a treat.
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Im using the 6" LED displays with the Sparkfun Large Digit Drivers. The relay is complete module with an optocoupler, apologies, I should have mentioned this. I was thinking of implementing a flyback diode for the motor but am not sure how they work or if I have the required diodes. Ive got a collection of zener diodes and a few 1N4007 diodes.
The 1N4007 can be used as a flyback. Just insert it, reverse biased, across the motor supply terminals (the cathode, with the stripe, goes to the positive terminal).
You can also add a ceramic capacitor across the terminal, in the range 0.01uF to 0.1uF to help control electrical noise.
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Gotcha! I will give it a try and keep posted. Thanks!
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