Low Voltage Cut Off

The low voltage cut off stops the batteries from draining too low.  Draining the batteries too low stops them from being able to recharge fully ever again.  

Below is a picture of the assembled LVCO.



Below is the circuit diagram for the LVCO.


The critical part of this circuit is the relay; the relay had to be of form B (which means normally closed), and fit the IV specifics.  This was difficult to find due to the low current specifications we have for this project.  

Here is a parts list for this circuit:

Materials	Manufacturer	Description	Amount per Model	Cost per Model
Relay	Claire	OptoMOS Solid State Relays SPNO SPNO 4 PIN SIP 1-FORM-B	1	$1.40
OpAmp	National Semiconductor	IC COMPARATOR QUAD LO PWR 14-DIP	1	$0.60
10k Potentiometer	Bourns Inc.	POT 1.0K OHM 1/2" RND WW SEAL ST	1	$9.54
1k Ohm Resistor	Radio Shack	1K Ohm 1/4-Watt Carbon Film Resistor (5-Pack)	2	$0.20
Zener Diode	Panasonic	DIODE ZENER 13V 150MW S-MINI 2P	1	$0.38
Board	Radio Shack	Dual Mini Board w/ 213 Holes	1	$1.99
Total				$14.11

To calibrate the LVCO, we took the following steps:

1. Set the voltage generator in the lab to 5.24 V (the minimum for the battery pack)  
2. Then connect the LVCO to the voltage source where it says V1 on the diagram.  
3. Turn the potentiometer until the relay switches off.  

Katie Gallo          kgallo@uvm.edu
Tom Lanagan     tlanagan@uvm.edu