Pic Ammeter

[Ingvar]

Maxim have several "current sensors", one that springs to mind is MAX4172.

[ero]

@rytech,
I have made similar system by using a pic. I explain you how it can be done.
The components;
1 pce. LM358 opamp
2 pcs. res. 1K 1/8 watt
1 pce res. 0R1 (0,1 Ohm) 5 watt or bigger.
1 pce. res. 6k8 1/8 watt.
1 pce variable trimpot 4k7

The schema can be loaded from following link.

http://rapidshare.de/files/10143993/ampoku.EMF.html

The output of the LM358 will be connected to ADC input of the pic.
The max. current which is the total capacity of your power supply, will be regulated by 4K7 trimpot. This circuit is arranged for measuring max. 5A current.
You can connect one ammeter serially to the circuit and connect also one current source (can be one auto-lamp) and regulate the total current by trimpot.

ERO

[RYTECH]

Thanks for your prompt suggestions, i will investigate both options and post if any trouble in implementation.

[RYTECH]

I've obtained several max4172 SOIC IC's. Could somebody help me get started with the current sense of my 12v source. The mesurable range should be between 0 and 1 amp (lets start with just metering the logic part of my project).

I will be using the 2nd A/D channel on my pic as the first is used to sense battery voltage.

what i need is a schematic with some explanations, the datasheet seems compllicated and doesnt explain how to interface to the pic.

Thanks

[AMay]

If you just want to measure the current, get 1% .1, 1 and 10 ohm precision resistors, put them in the circuit one at a time, and measure the voltage drop.

If you want a permament meter, use the .1 ohm, and get one of the cheap volt meters which run on a 9v battery. Set it accross the resistor, and set it to one of the low ranges.

Resistors are available from Mouser 71-RS5-.1 etc. I think Circuit Specialists has the best deal on Meters.

Good luck

[RYTECH]

can i get some more help interfacing the max4172 ic's... i'm having a hard time with figuring out what resistor values to use in my circuit

the input source voltage is 5v's the ammeter should be able to monitor between 0 and 2 amps.

[JIM A]

THIS CIRCUIT SHOULD DO WHAT YOU WANT. NOTICE THE INACCURACIES BELOW 40-50mA LOAD CURRENT. THIS COULD BE COMPENSATED FOR, BUT WOULD ALLOW LESS VOLTAGE FOR THE LOAD.






http://rapidshare.com/files/312322/MAX4172_EX.TIF