newbiie: Can i make this with adruino ?

Forum 2005-2010 (read only) General Frequently-Asked Questions
1

Hello i need to the following...

monitor a battery voltage, and it get's lower than 24v i would need to activate a latch relay to switch on the charger and when it get 30v activate the latch relay to turn off the charger..
And would be nice also to produce some beep alarm when it reaches the 24v ?
I would like to this wihout computer intervention, but also being able to manually force the relay by computer interface (usb) ..

Can this be done ?
thanks

2

Yes that is perfectly straight forward. Use potential dividers so that you maximum 30V is below 5V for monitoring.

3

Please, give some next steps i'm complete lost where to start...
what to buy, how to program ?

Thanks

4

Please, give some next steps i'm complete lost where to start...
what to buy, how to program ?

Ouch. Without any clue about electricity or programming, the easiest, fastest and cheapest way to get the desired function is to buy a finished black box on ebay that does what you need.

If you don't believe me, fine go ahead. Start out with one of those: http://arduino.cc/en/Main/Hardware
plus a collection of resistors, a few leds and a few general purpose transistors and diodes.
Then go ahead an learn to program it a little. A good stating point is here: http://arduino.cc/en/Tutorial/HomePage

Once you have that down pat, you can think about starting to solve the problem above. If you fool around with the 24V supply too early, there's a good chance you're going to fry your microprocessor.

Korman

5

hi, i have know how on programing (c c# & delphi), i'm also not zero in electricity..

just don't want go the wrong way because i just found the adruino..
i was looking at first on this "http://www.phidgets.com/" and they have the relay and the V sensor.
But it seem very expensive and they don't have the latching relay..

6

i have know how on programing

Then you would know that the program would be little more than

if (voltage < 24) {
   pulse_relay_set_pin();
   beep_alarm();
}

if (voltage > 30)
   pulse_relay_reset_pin();

Normally some hysterisis would be a good idea as well but in this case I don't think it matters as doing multiple pulses to the same latching relay pins won't do any harm.

As mentioned divide your input voltage by 6 so the Arduino sees 0-5v.

And for the PC interface read the RX line and test for one or more characters.

BTW, this could be done with a comparator or two or a single 8-pin ATtiny85, an Arduino is an overkill.

7

Hi, so what board is best:
Arduino Mega Atmega1280

or this one
Arduino Uno

Would this be ok for the relay ? i would prefer a latch relay can i buy one and connected it directly to the adruino ?
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=150495558944&fromMakeTrack=true&ssPageName=VIP:watchlink:top:en

Can y buy this one

http://panasonic-denko.co.jp/ac/e/control/relay/power/specdetail/index.jsp?part_no=ADJ13005

how to connected ?

i can't find the module to measure voltage.
How to connect this to the adruino ?

thanks

8

Both the mega and uno can be used for this, I would take the uno as it got plenty of pins for what you are making.

You can connect the arduino to the battery by using a divider like Grumpy_Mike said, you need to get the maximum voltage down to 5V for the arduino.

You can connect that to a analog pin, and get a 0-1023 readout (0-5V)