Modifying BC547 Battery Tester Circuit for 6V Lead Acid With 3 LED State Indicators

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#1 21659081 12 Jun 2011 10:28

John Builder John Builder

Anonymous

Post #1
21659081 12 Jun 2011 10:28

http://www.circuit-projects.com/battery/economic-battery-sufficiency-tester-by-bc547.html

Can this one be modified so 3 low power consumption
l.e.ds can be added, so they would show the state of a 6volt 4.2-4 amp lead acid battery, red for very low amber for low green for high, tried hobby shops, but they only have ready made testers with leds, which cant be modified so that I can have the leds coming out of the back of the boat, thanks for any help.
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#2 21659082 12 Jun 2011 12:31

John Builder John Builder

Anonymous

Post #2
21659082 12 Jun 2011 12:31

http://images.maplin.co.uk/full/l21ac.jpg battery

http://www.carpcatchers.biz/acatalog/Lakestar_Pocket_Rocket_Bait_Boat.html boat
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#3 21659083 12 Jun 2011 15:46

Cody Miller Cody Miller

Anonymous

Post #3
21659083 12 Jun 2011 15:46

Do you want the LEDs always on? Also are you more comfortable with an analog solution or a microcontroller solution?
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#4 21659084 12 Jun 2011 15:49

Cody Miller Cody Miller

Anonymous

Post #4
21659084 12 Jun 2011 15:49

I'm curious about this boat is it RC? And do you fish behind it?
#5 21659085 12 Jun 2011 16:29

Olin Lathrop Olin Lathrop

Anonymous

Post #5
21659085 12 Jun 2011 16:29

You don't need 3 LEDs to indicate 3 states. You could make a very simple tester with a red and green LED, for example. Nothing lit means tester is disconnected or battery is very low. Green means it's at least above the minimum threshold and red+green means it's above the upper threshold. In normal operation, you want green on and red off.

Now you only have to light two LEDs, each with its own threshold. For something very quick and dirty, you could use a voltage divider and the B-E drop of a transistor as the voltage reference. For more precision and temperature stability, use TL431 instead of transistors.
#6 21659086 13 Jun 2011 02:21

John Builder John Builder

Anonymous

Post #6
21659086 13 Jun 2011 02:21

I`m a complete novice, last time I did electronics was at 13 in school but I learn fast, maplins do a low consumption led, prefer them always on, that way I can see that its working even at distance on the water, red would be the lowest threshold, green highest amber in the middle, green goes out medium power, amber goes out low power, red , bring the boat in change the battery , I will take the boat apart and let you know what motors its running in a couple of hours, thanks for your replies so far
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#7 21659087 13 Jun 2011 02:30

John Builder John Builder

Anonymous

Post #7
21659087 13 Jun 2011 02:30

RC yes, you use it to put the bait at distances further than castable, upto 500yards
#8 21659088 13 Jun 2011 06:05

John Builder John Builder

Anonymous

Post #8
21659088 13 Jun 2011 06:05

MFA como drills torpedo 500 4.5 - 15 volt dc motors
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Topic summary

The discussion centers on modifying a BC547 transistor-based battery tester circuit to include three low-power LEDs indicating the charge state of a 6V, 4.2Ah lead acid battery used in an RC bait boat. The desired LED indicators are red for very low battery, amber for low, and green for high charge, with LEDs always on for visibility at a distance. Suggestions include simplifying the design by using two LEDs with voltage thresholds or employing voltage dividers and transistor base-emitter voltage drops as references. For improved precision and temperature stability, a TL431 voltage reference is recommended. The boat uses MFA Como Drills Torpedo 500 DC motors rated 4.5–15V. Low consumption LEDs from Maplin are preferred for the indicators. The boat is used to carry bait up to 500 yards beyond casting range.
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Modifying BC547 Battery Tester Circuit for 6V Lead Acid With 3 LED State Indicators

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Topic summary