Could someone please take a look at the pcb layout in the pic below and tell what if anything is wrong with it. I have already built this prodject once but on 2 seperate pcb's (1 for the powersupply and 1 for the control circuit) and it worked fine now that ive stuck it all on 1 pcb im getting problems, first LED 3 is on permantly even though it should only be on when SW3 is close it is also getting 7.2 volts when the circuit is run on 6
also LED2/1 glow dimmly when they should be off they are receiving 1.3v when it should be 0v,
I been trying to figure this out for the last 4 hours and am tearing my hair out.
thanks in advance
john
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1. Check what brand you have used for 2N7000 as there are many pin-out available. see their make, and cross check from relevant data sheet.
2. The Transformer is said to be 10:1 ratio. thus secondary would be 24AC and 34V DC At this voltage level 1K series resistor is low for the LEDs. Red LED drops around 1.4V across it.34-1.4=32.6V . This 32mA current flows thro each LED- I fear it is too much a current. you may limit it to 8to 10mA irrespective of color, by changing R2, R3, R4 to say 3k3 each.
3. If Neutral can be ensured by use of 3 pin plug at mains voltage, it would be better to direct the neutral wire and use 2 contacts in parallel on phase lead. this would ensure good contact when relay operates.
Also perhaps you need a spark quench in the form of R-C series across the contacts -- otherwise the relay contact would be short lived.
4. At 34V supply line, 1N4148 is inadequate for snubbing the back emf across relay coil. perhaps you may choose BA159 or any other such fast recovery diode of higher voltage.