Hey y'all! I'm an electronics student (my first year) and I'm managing a project with an arduino Nano (clone) in which I need to power several sensors, two infrared and one ultrasonic, as well as two systems of JQC 5v relays that control a 12v dc motor and a windshield wiper motor. I power all this from a 12V 12A SMPS so I dont think current supply is a problem (I've calculated to total approximate current load of the circuit and its around 6-7 Amps), and the sensors and relays with their respective 5v regulators (LM7805). What happens is that when I want to activate the relays, they work perfectly fine when they don't have a load attached to them, or when only one of them has a motor connected. However, whenever I connect both motors and make them work at the same time, the relays start working erratically and eventually get stuck on permanently on or off until I power off the board. This problem also interferes with powering my Arduino. Anything to guide me?
Motor specs
DC motor: 12V 12W
Wiper motor: 12V 18W
Attaching circuit schematic
I have seen wiper motors go above 10 amps, I do not know about yours but 18 watts sounds light. I appreciate your attempt at a schematic and I will guess you have not studied them yet. Simple thing I do is power top(+) down(-) and signals left(in) to right(out). Check this link: Simple electronic circuit for beginners | ElecCircuit.com I would suggest you look up the data sheet for your regulators, from the way you have drawn it they will not work and or fry. look closely at the caps.
im using LM7805 regulators. Sorry for the schematic, I drew something a bit crude in Proteus since I only had my schematics drawn in Fritzing. Still thanks for the advice. As for the wiper motor, I have it working at 12v as I said before and when I checked with a multimeter it only drew ~1.5 Amps at low speed (connected directly to the power supply, same as connected through the circuit board)
Did you read the manufacturer's data sheet for the 7805s you are using, they are not all the same. Did you check the link out? See if this link helps: 7805 Voltage Regulator Circuit | CircuitsTune . Why are they not teaching schematics the language of electronics?
We had been taught to express a source as a battery symbol most of the time. Still, I have only learned the basic use of Proteus a few days ago, and we were using either fritzing or a really basic software for schematic drawings/pcb design that wouldnt allow for custom libraries, so out of necessity I started teaching myself Proteus.
Anyways, for what I had checked, I can't see the problem with the way I connected the regulators (they work fine in the pcb, I'm using the TO-220 version of a 7805CV): Vi is connected directly to the power supply V+ (12V), GND to the V-, and Vo supplies on one regulator the relays, and on the other the Vcc pins of my sensors
Hi, @wxrcom
Can you please post a copy of your circuit a picture of a hand drawn circuit in jpg, png?
Hand drawn and photographed is perfectly acceptable.
Please include ALL hardware, power supplies, component names and pin labels.
In my opinion, the problem you are having could be caused by electrical noises generated by the relay contacts when activating the motors. (Spikes).
Motors are inductive loads, and generate high electrical noises when turning on and off.
I suggest that you use flyback diodes in parallel with your motors, to reduce the level of these noises.
Ref: " Flyback diode - Wikipedia
I redesigned my circuit for it to stop implementing the voltage regulators, as the +5V from the arduino proved to be sufficient for both the relays and the sensor (which I don't know exactly why it wasn't before, maybe faulty connections or somethng else entirely). I also changed the limiter resistors for each transistor to be of 1k instead of the previous 100k, and added the flyback diodes for the motors. I applied all of this observations onto a breadboard circuit and all of it works fine, as I intended originally. Really appreciate all the help you gave to me and I hope to learn from this and everything that comes my way in the future. Love y'all!
