Electricity Consumption Gauge

Elie

I'm trying to build a gauge that will display how long an appliance has been turned on. My idea is to connect the appliance's power source to a Basic Stamp as input and to connect a servo to control the gauge's needle as output from the Stamp. So, all the Stamp would do is start counting when it detects current from the input and use this count to move the servo to a certain position.

The problem is, I have no idea how to do this. I have worked with Basic Stamps a little but I've never done any interfacing with other devices. I don't know how a Basic Stamp could detect current or even if it's possible. If anybody could help me out with ideas, tutorials, or just pointing me to a good resource to help me make this project, it would be greatly appreciated.

Thanks!

Paulie

Elie,
Interface your appliance and stamp with a relay.The appliance would power the relay ,switching a stamp input to start your counter.Use a serial lcd display for the information indicator.Store accumulated information in the eeprom.

Bean

I did a similar project to time how long my oil furnace was on.

What I did was connect a neon bulb across the burner and glued a CDS cell to the neon bulb, then put the bulb and CDS cell in a light proof box.

You can easily measure the resistance of the CDS cell to see if the bulb is on or not.

Terry

allanlane5

'Bean':

Clever. You've built your own optically-isolated monitor which reveals
if the power is on or not.

OP: You don't really need to find the current, 'Bean's approach is
pretty non-invasive, and can be very safe.

basicstampede

I've done something similar.

I used a Current to Voltage transformer from a company called Instrument Transformers Inc. in Clearwater, FL.

Just feed a single wire which carries the current for the load you are monitoring.

The transformer provides output voltage (0 to 5 V DC) which I measure with ADC and have Stamp read the reading.

It works very well.

Only drawback:· The transformer is a bit expensive and a bit bulky (4" x 3" x 3").

·

Elie

If all I need to know is if the appliance is on or off, I don't really need that Current to Voltage Transformer, right?
I think the relay would be more adequate for this project without complicating things.

So, a couple more questions:
1) Is there a "relay chip" or "relay switch" or something that I can buy directly at an electronics store that I'll be able to put in a 120V AC circuit?
2) Is the relay output going to be 120V? Will I need a converter and transformer to reduce that to ~5V DC?
3) Any ideas on how to connect the relay to an appliance's power source? I think it would be ideal if I could get something that I could plug into a wall outlet, and then plug the appliance into that. That way it could plug into anything and be a more universal thing.

By the way, thanks a lot everybody.
I didn't really know what I was getting into when I posted this (I've never done anything like this before) and I guess it won't be as complicated as I thought.

ion

you can buy at any Radio Shack a relay and socket , with a coil rated to 120VAC. Conect the coil in paralel with your appliance, after the power switch ( the relay will turn on only if the appliance is on ), then take 5 VDC from the stamp board to the common of the normal open contact, then feed back the other side of your normal open contact to the stamp on an input pin.
ion