CirKits.com BVM1-a1 Battery Voltage Monitor Alignment Instructions Work with the board mounted on a non conductive surface, or mount the board permanently to a metal plate using spacers. You will need a 0-16VDC variable voltage power source such as a lab supply, the assembled Battery Voltage Monitor circuit board and a digital volt meter. The trimmer potentiometers have a full range of 25 turns, they make a clicking sound when they are at the endpoints. CAUTION: the first time the board is connected to the power source, it is advisable to make a brief connection to be sure that there are no high current shorts from the soldering job. Rechargeable batteries have the ability to produce large amounts of current and short circuiting them can cause fires. Remove metal jewelry when working with batteries. Keep exposed metal objects away from batteries. Quick Calibration Instructions: ------------------------------- For a quick but not very accurate calibration, adjust the resistances of the three trimmer potentiometers from the pot's center pin to the pin under the adjustment screw as follows: VR1 (Span): 620 ohms VR2 (Offset): 660 ohms VR3 (Beep V): 6.7K - beeper activates below 11V (approx.) After the quick calibration, you can connect the board to the variable power supply and check its operation. Accurate Calibration Instructions: ---------------------------------- Connect the BVM1 Bat - and Bat + connections to the output of a variable power supply (voltage source). Connect a digital volt meter to the BVM1 Bat - and Bat + connections. Low Voltage Beep Adjustment: ---------------------------- Set the variable voltage DC power supply to 11.0VDC, or to the voltage that you would like the board to start beeping at. Turn the Calibrate switch S1 ON (toward the center of the board). Turn the Beep On switch S2 ON (toward the center of the board). Turn VR3 (Beep V) counter-clockwise until the beep stops, then slowly turn VR3 clockwise until the beep starts. Adjust the variable supply above and below the beep turn-on point and fine-tune VR3 so that it starts beeping at the desired voltage. Lower the power supply voltage until the beep starts, turn the Calibrate switch S1 OFF. You should now hear a short beep about once every second. Voltmeter Adjustment: --------------------- Understand how VR1 and VR2 work: VR1 (Span) adjusts the voltage range that the meter responds to, VR2 (Center) adjusts the turn-on position for all of the LEDs in the LED array. Turn the Calibrate switch S1 ON (toward the center of the board). Turn the Beep On switch S2 OFF (toward the edge of the board). Adjust a voltage source between 0V and 16V, some or all of the LEDs should light up in sequence. The voltmeter calibration is much easier to perform if you have a voltage source that can quickly switch between the two calibration voltages, 10.5VDC and 15.0VDC. Two adjustable supplies and a switch can be used. Connect the voltage source to the BVM1 Bat - and Bat + terminals and set the voltage source to 10.5VDC. Adjust VR2 (Offset) CCW to CW until LED1 (10.5V) just becomes bright. Set the voltage source to 15.0VDC. Adjust VR1 (Span) until LED10 (15V) becomes fully bright. Alternate between the two voltage settings and repeat the adjustments of VR2 and VR1 again for a more accurate calibration. You can verify the calibration by comparing the LED turn-on points to the digital voltmeter readings while slowly changing the input voltage. That completes the alignment of the BVM1. BVM1 Board Mounting: The BVM1 should be permanently mounted in a metal or plastic box to prevent short circuits and the potential of a fire hazard. The BVM1 is designed to fit into a standard 4"x4" electrical utility box, it should be mounted on the 4"x4" box cover plate with four 4-40 x 1/2" screws and 1/4" long spacers. Holes should be drilled in the cover plate to allow access to the LEDs and switches. A piece of 4"x4" clear plexiglass makes a good substitute for the steel box cover, holes only need to be drilled for the switches and mounting screws. BVM1 Board Connection: The BVM1 should be connected to the battery via tinned stranded hookup wire. The wires should be color-coded black (-) and red (+) to avoid confusion. The tinned ends of the wires should be cut to about 1/4" so that no bare wire is exposed when the wires are inserted into the BAT connector. The BAT connector screws should be tightened snugly, don't over-tighten the screws or the connector will be destroyed. The BVM1 can be permanently connected to a 12VDC source such as a solar charged lead acid, NiCd or NiMH battery. If the battery is a long distance from the DAS1, a 1 amp fuse should be put near the power source to protect the wiring against shorts. The wiring should be routed so that it does not cross any sharp metal edges and the remote ends should be connected to the battery terminals. BVM1 Board Operation: Turn the Calibrate switch S1 OFF and the LED array will blink to indicate the battery voltage. Turn the Calibrate switch S1 ON and the LED array will remain on, this mode will consume slightly more battery current. The calibrate mode is useful for displaying quickly fluctuating DC voltages. All of the LEDs will turn off if the input voltage is below 10.5V and the white LED will stay on for all voltages above 15V. Turn the Beep On switch S2 ON (toward the center of the board) to enable the low battery voltage beeper. To disable the beep, turn the Beep On switch to the OFF position.