Welcome to the N1IR Electronics Website. Totally off the cuff, one take, unrehearsed video projects for anyone interested in amateur radio, electronic design, makers, hardware hackers and science.

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Training the hand and mind since 1982.

Thursday, February 17, 2011

Sealed Lead Acid Battery Monitor (SLAB_M)

Greetings all, Here is another one of my projects. Sealed Lead Acid Battery Monitor (SLAB_M). Basically this is a voltage comparator circuit. I used the LT6700, thank you linear technology for the samples! In the LT6700-3 there are two non-inverting comparators, in the data sheet they used two for a high/low battery condition, I just needed one so I paralleled them. This is for two reasons, first is any noise on a open input the second is I doubled my output current capacity from 5mA to 10mA of the op-amp. Supply range is from 1.4V to 18V perfect for a SLA 12V 80AH battery. Total quiescent current measured about 20uA, about one thousand time less than the natural decay of the battery sitting with no load. Total current with the buzzer in the trip state is around 5 mA. Once the voltage drops to 10.6 volts the buzzer will sound until the voltage rises above 10.6 volts. Hysteresis measure was very small about 5 mV, in fact I had a hard time measuring this with the equipment I have at hand, the characteristics on/off was so sharp. There was an error in the video I mentioned 60mA, I didn't see the decimal point it's 6mA when simulated. I used NI Multisim 10 for the circuit simulation and traxmaker 2000 for the PCB. Gerber file are available by email. There is a high voltage version that I used (LT6700HVHS6-3#PBF) the max input is 36 Volts. The CS Version at 18 Volts was kind of cutting it close in my final application with a solar cell charger (17V no load). Go and build something! N1IR de CJ..73's