LED Volt meter - I would like this circuit to indicate up to 15 volts

Hi all

Please help me, I would like this circuit to indicate up to 15 volts , what components should be added ?



**broken link removed** Here is a Simple LED Volt meter to Monitor the charge level in Lead Acid Battery or Tubular battery. The terminal voltage of the battery is indicated through a four level LED indicators. The nominal terminal voltage of a Lead Acid battery is 13.8 volts and that of a Tubular battery is 14.8 volts when fully charged. The LED voltmeter uses four Zener diodes to light the LEDs at the precise breakdown voltage of the Zener diodes. Dont forget the forward voltage drop of the LEDs. Usually the Zener diode requires 1.6 volts in excess than its prescribed value to reach the breakdown threshold level. Nonsense! The "designer" of this circuit has forgotten the forward voltage drop of the LEDs. The Vf of an LED depends on its colour and is not a well defined characteristic. Which makes this a bad circuit. When the battery holds 13.6 volts or more, all the Zener breakdown and all LEDs light up. When the battery is discharged below 10.6 volts, all the LEDs remain dark. So depending on the terminal voltage of the battery, LEDs light up one by one or turns off. LED Volt Meter Circuit Circuit diagram:LED Volt Meter Circuit Diagram LED Volt Meter Circuit Diagram Author: D. Mohan Kumar Copyright: electroschematics.com [URL="http://www.extremecircuits.net/2010/06/led-volt-meter.html
]LED Volt Meter Circuit Diagram[/url]

IDK much about zener's but if your circuit works, all you need to do is adjust the value of Resistors for sensitivity tuning, (use a POT!)

oh ya, and there is a short circuit after your capacitor which you should take out

The resistors merely set the brightness of the LED's, NOT the voltage they light at.

He would need to add a 13 zener, plus a suitable resistor and LED.

Also possibly increase the value of the other resistors to account for the higher voltages?, but it's probbaly not a concern.

buju357 said:

Hi all

Please help me, I would like this circuit to indicate up to 15 volts , what components should be added ?



**broken link removed** Here is a Simple LED Volt meter to Monitor the charge level in Lead Acid Battery or Tubular battery. The terminal voltage of the battery is indicated through a four level LED indicators. The nominal terminal voltage of a Lead Acid battery is 13.8 volts and that of a Tubular battery is 14.8 volts when fully charged. The LED voltmeter uses four Zener diodes to light the LEDs at the precise breakdown voltage of the Zener diodes. Dont forget the forward voltage drop of the LEDs. Usually the Zener diode requires 1.6 volts in excess than its prescribed value to reach the breakdown threshold level. Nonsense! The "designer" of this circuit has forgotten the forward voltage drop of the LEDs. The Vf of an LED depends on its colour and is not a well defined characteristic. Which makes this a bad circuit. When the battery holds 13.6 volts or more, all the Zener breakdown and all LEDs light up. When the battery is discharged below 10.6 volts, all the LEDs remain dark. So depending on the terminal voltage of the battery, LEDs light up one by one or turns off. LED Volt Meter Circuit Circuit diagram:LED Volt Meter Circuit Diagram LED Volt Meter Circuit Diagram Author: D. Mohan Kumar Copyright: electroschematics.com LED Volt Meter Circuit Diagram

Click to expand...

All in all this is a bad circuit which will probably be very frustrating to try and duplicate.
You would be better of using a circuit based on an LM3914.

IDK much about zener's but if your circuit works, all you need to do is adjust the value of Resistors for sensitivity tuning

Click to expand...

Completely wrong!
As Nigel mentioned as I was typing a higher voltage zener is required, but this is still a bad circuit.

I am not convinced that the capacitor is doing any useful function either.

And yes, as drawn the circuit has a short circuit between the +ve and -ve lines.

JimB

is that because the zener is off and charges right to full volts(note he has it reversed bias)? what if he put resistor(R5) from r1 to gnd? wouldn't that create a ref voltage to switch the zener I/O,,

He has R1,2,3,4 values incrementing brightness, he should set them the same,no? New R5 would be reference?

This is a really dumb circuit!
First, it is impossible to keep the LED brightnesses matched at different battery voltages.
Second, the damn thing will kill a 50AH battery in less than a month just due to the current it takes to operate it.
Third, the turn-on voltage for each LED is the sum of the Zener voltage and the forward drop of its respective LED, making it hard to select the steps.

Look at the simulation of just two Steps, using a red and green LED. Note the soft turn-on knee, rather than a nice steep rise in LED current as the voltage increases. Also note that the turn-on threshold is the sum of the Zener voltage and the LED forward voltage drop. Finally, note that the current-limiting resistors have to be selected for each LED.

Dump this crappy circuit and get an **broken link removed**