I'd like to create a max 100A digital ammeter and voltmeter w/ LCD display using an Arduino for a RC battery charging case. I know I'd need to use a current shunt for current, but I'm wondering how one would go about such a project. Since the I/O pins are max 5v, how would one measure up to around 36VDC with an Arduino? And how would you use the shunt to calculate current with the Arduino?
Google "voltage divider" to find out how to reduce the voltage. You may need something more complex because the voltage range that is interesting for charging batteries is quite small and you need good resolution in that range.
There are a large number of current shunts built into easy-to-use chips. Have a look at what Sparkfun and Adafruit have.
Of course there are dedicated battery charger chips available that do all of this, as well as the hard maths so building an Arduino battery charger is just a learning experience.
Since the I/O pins are max 5v, how would one measure up to around 36VDC with an Arduino?
[u]Voltage divider[/u], plus [u]protection diodes[/u] to protect against unexpected voltages.
KpilotRCHelis:
I'd like to create a max 100A digital ammeter and voltmeter w/ LCD display using an Arduino for a RC battery charging case.
You've got me very curious how you're going to power a charger capable of 100A at 36V. I'm pretty sure that much power would blow a fuse on a normal household outlet. Maybe an outlet intended for a large appliance could handle that much power?
Sorry for the late replies. I've been busy with other stuff.
MorganS:
Google "voltage divider" to find out how to reduce the voltage. You may need something more complex because the voltage range that is interesting for charging batteries is quite small and you need good resolution in that range.There are a large number of current shunts built into easy-to-use chips. Have a look at what Sparkfun and Adafruit have.
Of course there are dedicated battery charger chips available that do all of this, as well as the hard maths so building an Arduino battery charger is just a learning experience.
Sorry if I was not clear. The Arduino will not be charging, just monitoring current and voltage. See below.\
DuaneDegn:
You've got me very curious how you're going to power a charger capable of 100A at 36V. I'm pretty sure that much power would blow a fuse on a normal household outlet. Maybe an outlet intended for a large appliance could handle that much power?
The charger is a commercial RC battery charger, the iCharger 3010B. Capable of up to 10 cell Lithium Polymer/Ion batteries at up to 30A charging current (but a max of 1000W so current will be limited with higher cell counts).
Power supplies are the HP DPS1200FB 1200W server supplies, two/three of them for 24v/36v respectively. Total charging power with that charger is 1000W max, but there are some chargers capable of well over 1400W (iCharger 4010 Duo for one example), when using 36v power supply setup.
Replying to both your posts, the charger will never pull 100A... but like I said I want headroom in case it gets close.
Also, the unit will not be measuring the actual charging current but the total current being pulled from the supplies (Main charger, plus any external chargers I may have hooked up to it, 12v to 5v USB adapters, PC fans, all for and in the case.)
It will also be monitoring voltages (hence the voltmeter I want) coming from the power supply setup making sure it's stable.