Posts Tagged ‘Automotive Voltage Indicator’

Components Voltage Tester Circuit Schematic

This simple circuit tests speakers, microphones, transformers and voltage. It’s basically a very low frequency oscillator that produces extremely short ‘fruity’ pulses. The type of sound produced is very easy to hear and to determine the precise direction it is coming from, thus making it ideal for checking the phasing in multiple speaker installations. It is also very useful for car stereo installations as well as public address systems where it can drive dozens of speakers directly on a 100V or 70V line system.

The signal is also easy to hear on a public address system so that you can drive around a large installation with the window down and easily hear each speaker as you drive past. It is easy to check that a speaker is in phase with its neighbours, by listening for the artificial centre created between two identical sound sources. Q1 and Q2 oscillate when connected to loads between zero and about 1000O. The frequency increases as the resistance of the load increases – loads produce about 8Hz output while 100O loads will produce about 100Hz output, although it is only approximate.

The unit is also useful for checking dynamic microphones (not condenser types), headphones, transformers (both audio and mains) and resistance loads (only visual checks via the LED). The pulses produced can sound too loud for some delicate circuits such as dynamic microphones and headphones, but the pulse is so short that it is virtually impossible to do any damage; the average current flow is only a few milliamps.

The circuit needs no power switch as the oscillator only operates when the negative side of the battery is connected through the load being tested. The LED flashes at each pulse as a visual indication that the load is lower than about 1000O. The circuit works from a 3V battery pack. To use a 9V battery change the 15O resistor to 47O, the 1.8O resistor to 5.6O and the .033µF capacitor to .01µF. LED2, diode D3, zener diode ZD1 and the series 220O resistor form a voltage indicator which is used to detect and indicate any voltage greater than about 10V.

LED2 only illuminates if the voltage rises above the threshold set by ZD1 and D1, which is more than the battery voltage (3V or 9V). These components can be omitted if the device is not going to be used for working on cars. However, it’s quite handy having a device that can check power wires, shorts to chassis and speakers in a car.

Parts:
R1 = 5.6M
R2 = 1.8R
R3 = 15R
R4 = 220R
Q1 = BC327
Q2 = BC337
D1 = Green LED
D2 = Red LED
D3 = 1N4148
Z1 = 6.8V Zener
C1 = 0.033uF
B1 = 3V Battery
read more : http://www.extremecircuits.net/2010/01/components-voltage-tester-circuit.html

Automotive Voltage Indicator

Connecting this circuit to the battery of your vehicle, you will always know at a glance the approximate voltage available.
An indication of battery voltage is useful to the motorist for monitoring the battery’s capacity to deliver current, and as a check on the efficiency of the dynamo or alternator.
Threshold voltages of the LEDs are set by means of two Zener Diodes (D6 & D10) plus two further Diodes wired in series (D4, D5 and D8, D9 respectively) adding a step of about 1.3V to the nominal Zener voltage.

LED indication:

* Red LED D1 is on when battery voltage is 11.5V or less. This indicates a low battery charge.
* Amber LED D2 is on when battery voltage is comprised in the 11.5 – 13.5V range. This indicates that the battery is good if the motor is off. When motor is running, this indicates no charge from dynamo or alternator.
* Green LED D7 is on when battery voltage is 13.5V or more. This indicates a normal condition when motor is running and dynamo or alternator are charging.

R1,R3,R6________1K 1/4W Resistors
R2____________100K 1/4W Resistor
R4,R5,R7,R8_____3K3 1/4W Resistors

D1__________Red LED (Any dimension and shape)
D2________Amber LED (Any dimension and shape)
D3,D4,D5_____1N4148 75V 150mA Diodes
D6_________BZX79C10 10V 500mW Zener Diode
D7________Green LED (Any dimension and shape)
D8,D9________1N4148 75V 150mA Diodes
D10________BZX79C12 12V 500mW Zener Diode

Q1,Q2_________BC547 45V 100mA NPN Transistors
Q3____________BC557 45V 100mA PNP Transistor

Read more source:http://www.redcircuits.com//Page115.htm
Thank you.

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