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Topic: Bus Pirate v4 high voltage interface (Read 1444 times) previous topic - next topic

Bus Pirate v4 high voltage interface

Hi All,

I have a pool controller that I would like to control.  Research thus far (based on chips on the pcb etc) has led me to believe its running a serial interface, possibly RS485.

However, as its designed for long runs its using 33VDC with respect to GND.

I realise I could direct connect to the main CPU, but its a pain to work in or around the pool equipment enclosure.
And if I do eventually make my own interface it will need to be able to send/receive at 33V.

So, my long question is:
Is there some simple circuit I can build that will shift/scale incoming data from 33V down to say 3.3V (or 5V) and do the opposite when sent?

I tried figuring out how the pool controller is doing it, but some of the chips and components are unreadable for manufacturer markings.  This may be deliberate, or could simply be because its been out in the elements for many years.

Thanks,
Matt.

Re: Bus Pirate v4 high voltage interface

Reply #2 –
[quote author="USBEprom"]Hi doozer.
I am not a great expert in that, but I think that could be possible to use something like the MAX485:
 
Be seeing you.

U.Sb[/quote]

Thanks, but the MAX chip seems to expect a line voltage of around 12V.

Looking at the controller PCB, my best guess is its doing some sort of voltage divider on the input and using a transistor to raise the output level from TTL to 33V.