Automated Watering with Attiny85 - Relay with too less power ?!?

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You don’t show the wiring on the bottom of the board so it’s hard to tell if the wiring is correct.

Are the wires color-coded in any useful way? It looks like Brown is Ground but Orange can’t be 12V because there is an orange wire connected to the ATtiny.

The symptom indicates a resistance between +12V and the output. There should be nothing between +12V and the output except the relay contacts. If that is true the relay may be faulty.

You have a resistor between the relay contacts and ground. Get rid of it.

Your circuit is also lacking the essential capacitors on the input and output of the voltage regulator, and a decoupling capacitor for the ATtiny.

dc42:
Your circuit is also lacking the essential capacitors on the input and output of the voltage regulator, and a decoupling capacitor for the ATtiny.

It also seems to be missing a flyback diode for the relay coil.

You can use the same (ceramic) capacitor to serve as both the output capacitor for the 78L05 and the decoupling capacitor for the ATtiny, if those components are close together.

In the diagram above, you appear to have put the flyback diode in series with the relay coil instead of in parallel. There also appears to be a capacitor in series with the coil.

Your capacitor values are OK, as you say they are as shown in the datasheet. If your supplier doesn't stock 0.33uF then use a higher value, such as 0.47uF or 1uF. The datasheet says that the output capacitor is only to improve transient response and not for stability, so you can leave it out and just have a 0.1uF or greater ceramic decoupling capacitor near the ATtiny.

The flyback diode needs to be in parallel with the relay coil, oriented so that no current flows through it when the relay coil is energized.

Still not quite right, the diode is shorted out. The anode is correctly connected to ground, however the cathode (with the stripe) should be connected to the junction of the relay coil and the ATtiny output.

btw I would have used a mosfet instead of a relay to switch the pump. However, that relay is OK because it only takes 30mA coil current, which is within the 40mA output current pin limit of the ATtiny.

I suggest you also connect a flyback diode (1N4001 or similar) in parallel with the pump, to reduce arcing and prolong the life of the relay contacts.

Your 10k pull-up resistor is wired as a pull down resistor.

-jim lee

The 1N4001 diode is connected incorrectly The cathode should be connected to +12V, not to ground. Other than that, it looks OK to me. Good luck!