Hi,
Would like to use a MAX8212 to switch an device on or off.
I got this picture from "Making things Talk". They used the MAX8212 with a Solarcell and an Xbee.
I tried to calculate the trigger voltage, the voltage on which the OUT Pin goes LOW. I got a Value of 1.265v but this can't be true can someone help me?
This is the circuit:
Basically, the circuit you show is a resistor voltage divider (10K, 100K) used to produce 1.15V at the desired trigger voltage. Based on those values... it's easy for me to see the same results you got... but the device will not operate at less than 2 volts... so it's clear why you say "it can't be true."
BTW: What are you trying to accomplish?
Anyway... this might help.
There is a neat spreadsheet for this device... here--> http://www.iamwhen.com/uploads/documents/robotics/Max8212SolarEngine.xls
thx
I got a solarcell (5v 300ma). This should charge a Lipo with the Lipo charger from Sparkfun SparkFun USB LiPoly Charger - Single Cell - PRT-12711 - SparkFun Electronics
So I like to trigger the voltage around 4.2V.
With your ExcelSheet R1,R2,R3 are something like:
R1: 10kOhm
R2: 16.1kOhm
R3: 10.4kOhm
Am I right?
Thx
Andy
To be fair: http://www.iamwhen.com/archives/53-Herbert-1701-Species-B-Generation-1.html
It's HIS spreadsheet. I just nicked it to give you a hand.
I'd say you are on the right track.
His page is worth a read... and he might be describing just what you need.
Why don't you just use your Arduino to figure that out? You can measure the Arduino's power voltage using the "bandgap" input of the ADC and back calculate to determine Vcc. You may need to calibrate your device, because the bandgap is not all that accurate. No extra parts, just a bit of code.
True... the MAX8212 is a glorified Comparator with some added trash... you have one built in to the AVR
no, I can't use it because my Arduino is built into a Weather Station. Just every ten minutes it sends Data over an Xbee and after that it goes sleeping 