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[on:]

Hello,

So I'm working on my first project which is an RFID enabled pet fountain. I'm trying to turn on and off an AC impeller aquarium pump based on what rfid tags are present. I'd rather not get involved with working with main voltage so I was wondering ss there any way I can power this impeller from DC? Ideally, from a 12v power supply or from the arduino 5v power. The AC impeller pump uses 230VAC 50hz. I'm pretty sure it has a tiny power draw. Anyone have any suggestions?

Thanks!

[Reply #1 on:]

If a motor needs AC it can't be run directly off DC. You can use a solid state relay to switch AC safely from your arduino.

Turning DC into AC is possible but is more tricky to design and expensive to do, especially as you only need low currents.

[Reply #2 on:]

You can buy an inverter to produce 230v from 12v, see for example http://uk.rs-online.com/web/p/dc-ac-inverters-battery-voltage/5388759/ (there's also a version with a UK socket). However, I agree with Mike that using an AC SSR to switch 230v is a better solution. Make sure that the SSR is suitable for switching the inductive loads (some are not) and the low current that your pump requires (AC SSRs have a minimum current they are happy to switch).

[Reply #3 on:]

Hello, new question:

I went to the electronics shop and bought an SSR and a screw terminal. I was wondering can I mount these components on a stripboard? If I do how would I mount the stripboard inside an enclousure. I assume putting metal screws through the strip board would be a bad idea? Any alternative suggestions as to how I should hook everything up safely?  Thanks

[Reply #4 on:]

You can put metal screws through a stip board provided that you make breaks in all the tracks that might connect the screw (or washer, nut etc.) to the circuitry, so that the two are isolated. However, bear the following in mind that if there is 230v anywhere on the strip board:

- If you do use metal screws and they can be touched by someone using the device, then those screws must be earthed to mains ground. Maybe you're planning to put the whole thing in an earthed metal box anyway.

- When using 230v on a stripboard, the spacing between strips is rather small for that sort of voltage. I would remove the strips either side of each 230v strip. You can do this by heating them with a soldering iron, using a knife to lift one corner of a copper strip and then tweezers to peel the strip off, all the time using the soldering iron to heat the right bit of the strip.

- When using a drill to make a break in a track, check with a magnifying glass that you really have made a clean break. I once had a tiny sliver of copper left after I made a break, causing the circuit to malfunction and damage components.

Alternatively, avoid putting 230v on the stripboard. If the SSR is the single-in-line type, you can probably use a plastic terminal block to connect to it instead.

[Reply #5 on:]

If you have a SSR like one of these: http://arduino-direct.com/sunshop/index.php?l=product_detail&p=216
then locate it near the pump, and run just 2 wires to you electronics section to turn it on. 

Cover the 230V terminals (Some come with a small plastic cover).. even tape over them , for safety if somehow exposed..

DISCLAIMER: Mentioned stuff from my own shop...

[Reply #6 on:]

If you need to pump water, look at getting something DC powered like below. If you need to pump air, bait shops have battery powered aerators like bottom.

http://www.harborfreight.com/floating-solar-fountain-pump-91962.html

http://www.google.com/search?hl=en&num=100&lr=&ft=i&cr=&safe=images&gs_sm=e&gs_upl=5968l5968l0l6765l1l1l0l0l0l0l235l235l2-1l1l0&q=aerator%20battery&um=1&ie=UTF-8&tbo=u&tbm=shop&source=og&sa=N&tab=wf

[Reply #7 on:]

Thanks for all the help. I'm going to see if I can get some terminal blocks (as it is SIL). Thanks again!

[Reply #8 on:]

The higher is better.

? 

So you are going to use your Arduino in a situation where 2KV is not enough isolation???

[Reply #9 on:]

Yer so you are going to dangle an antenna off it then?
I said:-
So you are going to use your Arduino in a situation where 2KV is not enough isolation? Let me add and that 7.5KV is, or in fact any achievable isolation?

You are not going to survive a direct hit no matter what isolation you have.

[Reply #10 on:]

@sonnyyu
I don't know what you think you are adding to this forum, I have seen several of your posts now and none of them make much sense and all of them are no help.

[Reply #11 on:]

@sonnyyu
I agree with Grumpy Mike. Please refrain from posting if you haven't got anything meaningful to add to a thread.