Hi all,
I have a machine running three 12v solenoid coils. Currently, control is carried out by manual switching of the negative through SPDT toggle switches. The coils all have a positive 12v common.
I am wanting the ability to additionally control the coils through Arduino with serial comms. As such, I have built a basic PCB consisting of a Nano, N channel Mosfets, diodes, voltage reg etc. I have then retrofitted this PCB into the existing machine wiring using a DPDT toggle ON-ON switch (see attached - apologies on the horrendous drawing!! Should do the job though).
When I flick the DPDT switch to power the nano I can successfully control the coils through a basic program. Mission accomplished.... or so I thought.
Initially I was getting a 0v leak through the voltage reg causing the coils to energise slightly (in manual mode), but wiring the voltage reg 0v to switched 0v fixed this.
When controlling the coils manually through the SPDT toggles, there is a back feed into the PCB (via mosfet drain i think) which lights up the LEDs on the Nano as long as the toggle switch is held. This caused the Nano to get hot, smoke and fail.
Is there a way I can provide some sort of back feed protection to the Mosfet drains when operating the coils through the manual switches? I thought of using diodes with anodes to drain and cathodes to coils, but then I stop the 0v return to battery when trying to operate the PCB.
I cant help but feel this would be much easier if switching the positive, but unfortunately in this case this is not an option.
Any help on this would be greatly appreciated.
Thanks in advance.
I have a machine running three 12v solenoid coils. Currently, control is carried out by manual switching of the negative through SPDT toggle switches. The coils all have a positive 12v common.
I am wanting the ability to additionally control the coils through Arduino with serial comms. As such, I have built a basic PCB consisting of a Nano, N channel Mosfets, diodes, voltage reg etc. I have then retrofitted this PCB into the existing machine wiring using a DPDT toggle ON-ON switch (see attached - apologies on the horrendous drawing!! Should do the job though).
When I flick the DPDT switch to power the nano I can successfully control the coils through a basic program. Mission accomplished.... or so I thought.
Initially I was getting a 0v leak through the voltage reg causing the coils to energise slightly (in manual mode), but wiring the voltage reg 0v to switched 0v fixed this.
When controlling the coils manually through the SPDT toggles, there is a back feed into the PCB (via mosfet drain i think) which lights up the LEDs on the Nano as long as the toggle switch is held. This caused the Nano to get hot, smoke and fail.
Is there a way I can provide some sort of back feed protection to the Mosfet drains when operating the coils through the manual switches? I thought of using diodes with anodes to drain and cathodes to coils, but then I stop the 0v return to battery when trying to operate the PCB.
I cant help but feel this would be much easier if switching the positive, but unfortunately in this case this is not an option.
Any help on this would be greatly appreciated.
Thanks in advance.