im not sure if this is an issue or not but i have developed a prototype circuit on a breadboard and now i want to send the pcb off for fabrication, however im worried if my diode configuration on my cad might be wrong. as the output from the transistor is connected to the diode then to the relay. my main issue is that the diode will draw the current and not reach the relay. i have attached an image of my cad design, so if anyone can look at it and tell me that it will work like that, i would be so grateful
That image is useless... Bunch of traces without reference. Please post a image of the schematic.
But to try to answer a bit, the diode should be anti-parallel to the relay coil. Aka, parallel but in the blocking direction (cathode to positive side).
septillion:
That image is useless... Bunch of traces without reference. Please post a image of the schematic.
But to try to answer a bit, the diode should be anti-parallel to the relay coil. Aka, parallel but in the blocking direction (cathode to positive side).
i will attach the full schematic, its just need to know if the traces from the GND from the transistor and 5V should go through the diode or do i attach the GND from the transistor and 5V to the relay and extend the traces from the output from the transistor to the diode.
i have attached another image called config and was wondering if my traces for my full schematic wont work for the diode to the relay would this one work
Your diodes are correctly across the relay coils, cathode to +ve supply.
But your power traces are too thin and routed rather oddly. Power traces should be low
inductance, ie wide, and preferably direct to the load and over ground-plane. You have a
worrying long path from load to decoupling capacitor for the relay loads and no decoupling
for the ATmega chip which may mean nothing works, or its flaky, or it works for months and
then stops at random, or almost anything.
Decoupling is not optional for logic chips, its an essential requirement. 0.1uF to ground on
every supply pin as close to the chip as possible.
