Have chased unit working the way I wanted. Ft
Just having a prob with mosfets.

I have the outputs from ic4017 connected to the gate of the stp55nf06l

The drain is connected to the power supply. ( 9 ) volts

The source of connected by to the strings of leds.

Nothing happening. Any suggestions as to why please

For an NMOS, the source should go to negative supply, gate to 4017, drain to LED cathode, LED adode to limit resistor, other end of resistor to positive supply.

 

Usually for a mosfet to switch on there must be a gate voltage relative to the source. With the source connected to the LEDs that are then connected to common, the very small leakage current will allow the source voltage to rise to the gate voltage, and thus no conduction because of no voltage difference.

Connect the positive end of the 9 volt LED string to the 9 volt positive supply and the negative end of that string to the mosfet drain connection. Then connect the source to the common and the LEDs should receive the 9 volts when the gate is driven.

 

The stp55nf06l is an N channel MOSFET. You have it’s connections reversed.

it should be connected to the cathode end of the LEDs. The drain should be connected to the LEDs. The source should be connected to ground.

 

The stp55nf06l is an N channel MOSFET. You have it’s connections reversed.

it should be connected to the cathode end of the LEDs. The drain should be connected to the LEDs. The source should be connected to ground.

That seems tobe what I said in the previous post, #42

 

That seems tobe what I said in the previous post, #42

Yeah, but it didn’t show up when I was typing my post. Sorry

 

That seems tobe what I said in the previous post, #42

And is what I said in #41.
But you forgot to mention the limiting resistor..