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power supply for raspberry pi + piface + sensors

Former Member

Hello,

 

I was considering buying a raspberry pi + piface + delta sigma adc, plan is to use them to control a few small power AC water pumps, and sample a few sensors with the ADC. The raspberry requires 5v DC, the sensors I believe anything between 8 and 30v, the piface seems to have a plug for an external power supply as well?

 

Here's the questions:

1) stacking piface and delta sigma adc, has anyone tried that? experiences? I'm pretty new to raspberry and friends.

2) do I need to connect the piface to an additional power supply to control the relays?

 

And here's the main problem...

 

I'm planning to assemble everything in a small enclosure, and have a single power cord go from the main to this enclosure.

 

There is no space for a normal micro usb charger + some other power supply + wiring to get the main into the relays and out to the pumps into the enclosure.

Ideally, I'd like a single cable from the main, use a terminal board to get the power to the relays, and from there into a single power adapter that gives me he 2 voltages needed for the raspberry / piface / and sensors.

 

So.. any suggestion for a suitably small power supply? AC as input (ideally both 110 and 240). I was thinking of two DC outputs, +5 and -5? attach the sensor and mod-io to the -5 and +5, attach the raspberry to +5 and ground. Does this sound reasonable? any suggestion of a small power supply to order / buy for cheap? any alternative?

Ideally with terminals to screw the wires to it easily and safely.

 

Note that I have some software experience, but have not done anything with electronics, so don't be afraid of suggesting obvious solutions I may have missed image

 

Thanks

  • Personally, this is what I would do.

    1. Acquire a +9V or +12V supply (this is comfortably above 8V for your sensors).

    2. Either construct or purchase a +5V DC-DC converter. This can power your R-pi and (presumably the Piface - not sure what voltage that needs). This one is quite low cost.

     

    If you want everything in the same enclosure, then you have to take quite a bit of care. So, it may be simpler to just have an external +9V or +12V DC supply, and just the +5V DC-DC converter inside your enclosure.

     

    If you really want it all inside one enclosure, then something like this +12V DC supply might be suitable, although you may want one with slightly higher power capability. You can see they are sometimes more expensive than an external supply. You can also get dual-output ones, but they may be even more expensive. If you're going the route of having it all in one enclosure, then you need to have some safety considerations, and often the easiest method of that means also purchasing an IEC type of socket with a built-in fuse and switch (expensive too).

    Since you mention cost concern, I'd suggest the external +9V or +12V supply method, with a small +5V DC-DC converter inside your box.

  • in reply to shabaz

    Great suggestion, thanks! Will probably go with those components.

  • in reply to shabaz

    For bench supply and larger metal cases there is the option of COTS PC power supplies.

    PC AT power supplies have these voltages on a molex connector. How to convert to microUSB?

    Are there peripherals/exansion boards  that take molex or screw terminals straight up without having to convert to USB? My EE friend told me the usb cable was too long. Obviously the 28 gauge wire is too small too.  A short 18 gauge power supply wire would be superior.

  • in reply to shabaz

    For bench supply and larger metal cases there is the option of COTS PC power supplies.

    PC AT power supplies have these voltages on a molex connector. How to convert to microUSB?

    Are there peripherals/exansion boards  that take molex or screw terminals straight up without having to convert to USB? My EE friend told me the usb cable was too long. Obviously the 28 gauge wire is too small too.  A short 18 gauge power supply wire would be superior.