Replace microswitches with mosfets (or something)

[fenderman]

Hi All,
This is primarily related to model railway point control.
A servo is used to operate the Point for its two directions, usually, the 'frog' of the point switches polarity by way of a mechanical switch (generally a micro switch)and maybe a second micro switch is used to change signal indications (red/green etc.)
These switches generally fitted to the track board, so the point itself operates the micro switch.
I want to move these switches off the track board an onto the PCB with the Servo.
This is where the problem comes, as the travel on the Servo can be different for the different track gauges, and if the Servo is to be used for something other than Points, the travel could be up to around 110 degrees; hence the mechanical micro switches would impede the servo movement.

My thoughts were to use a slotted Opto coupler to control a power (around 2A to 3A) MOSFET circuit that would operate as though it were a DPCO (Double Pole Change Over) relay.
The Servo would use a 'half moon' shaped actuator for the slotted Opto detector, hence no obstruction to the servo travel.

So, the question is: Is there any way of connecting (I assume 4) Mosfet’s to operate in this way ?
Oh, and also, to make things a little trickier, one of the pairs (the pair that switches the point frog) needs to operate in both polarities where the loco is travelling forward or backward.

I realise I could just fit a relay with a driving transistor from the Opto, but at 5v the current required when several point servo's would be used all with relays would be quite high, so hence was thinking along the 'solid state' lines.

You comments would be appreciated.

Regards
Roy

 

[Roff]

I suspect you are not getting any replies because you are using terminology that most of us are not familiar with (point, frog). When asking questions, you need to put yourself in the readers' shoes. Try to explain your problem in layman's terms.

 

[fenderman]

Cheers Ron,

I wondered if I may have gone too deep into the reason, rather than asking the question outright.

I have ordered a few devices to 'test to destruction' on a few circuit idea's I have and see what results I get.

I will leave the post for the time being, and maybe post again at a later date if I don't manage to sort it.

Thanks again

Roy