The circuit below is for a solar panel charge controller. It monitors the battery voltage and once the battery is fully charged, a relay activates a dummy load to drain the battery down to a safe level.

The battery status LED's are working correctly and everything seems great except that the relay is not activating. Only the red LED is being lit. When the red LED is lit, the relay should activate, kicking over power to the dummy load.

Could someone suggest to me why the relay is not activating?? Any help is MUCH appreciated!!!

 

The Mosfet is a P-channel. But the circuit needs an N-channel Mosfet for it to turn on.

 

I just found the issue. I left out the stupid 560ohm resistor (R4). I just added it and now it works fine. I've been driving myself crazy on this for 3 days now!

 

Audioguru,

It is an N-channel MOSFET. Contrary to BJT, the arrow should point inside for an N-channel, and outside for a P-channel.

 

I just found the issue. I left out the stupid 560ohm resistor (R4). I just added it and now it works fine. I've been driving myself crazy on this for 3 days now!

Only the red LED is being lit.

Its your own words against you.

The R4 is in series with the RED led. How can the LED being lit without a series resistor?

In addition, the stupid R4 would not prevent the relay from operating.

 

Our OP meant that they didn't connect R5 to the gate of the MOSFET. If you look closely at the schematic, you'll see that they are close together, but there is no actual connection.

 

Our OP meant that they didn't connect R5 to the gate of the MOSFET. If you look closely at the schematic, you'll see that they are close together, but there is no actual connection.

You have good eyes
I could not see it

Rifaa

 

I notice you are using a PICAXE 08M microchip. Do you have the code?

 

When I searched for the datasheet of an IRF610, the first one on the list was an IRF6100 which is a P-channel Mosfet.

I hate to see parts drawn upside-down. Positive is supposed to be upwards.

 

I notice you are using a PICAXE 08M microchip. Can you supply the code?