Automobile charging circuit light circuit

[Wayne Meglan]

I am new to circuit design, so please excuse my basic questions. I am trying to add a charging circuit light to my motorcycle similar to what we all have on our cars. I downloaded the attached circuit which accomplishes this. However, this design is for an alternator on a 12 volt system. I have a generator with a 6 volt system. It is my understanding that car alternators change the voltage to DC, so if that's true, the attached circuit should be ok for a generator. However, to modify this circuit to 6 volts, do simply do the following:
- use a 16 ohm resistor at 1/2 watt instead of the 33 ohm at 1/2 watt
- use two 510 ohm resistors at 1/4 watt instead of the 1K ohm at 1/4 watt
- use a 16 volt TVS diode instead of the 24 volt TVS diode (this is the spike protection circuit)
- use a 6 V Zaner instead of the 12 volt.

Thanks.

 

[Wayne Meglan]

I am new to circuit design, so please excuse my basic questions. I am trying to add a charging circuit light to my motorcycle similar to what we all have on our cars. I downloaded the attached circuit which accomplishes this. However, this design is for an alternator on a 12 volt system. I have a generator with a 6 volt system. It is my understanding that car alternators change the voltage to DC, so if that's true, the attached circuit should be ok for a generator. However, to modify this circuit to 6 volts, do simply do the following:
- use a 16 ohm resistor at 1/2 watt instead of the 33 ohm at 1/2 watt
- use two 510 ohm resistors at 1/4 watt instead of the 1K ohm at 1/4 watt
- use a 16 volt TVS diode instead of the 24 volt TVS diode (this is the spike protection circuit)
- use a 6 V Zaner instead of the 12 volt.

Thanks.

Please ignore the left side of the diagram. My circuit is on the right 2/3 rds of the page.

Thanks.

 

[CDRIVE]

First off I will tell you that I spiced your circuit. To get it to work at all you will need a variable resistor connected between Q1 base and GND. Even then this circuit could be replaced with a comparator with far better stability over temperature.

A 555 can be used as a comparator by jumping the Trig & Thld inputs.

EDIT: The 555 statement is not accurate. It can be used as a settable Schmidt Trigger not a Comparator. Though this is not accomplished by tying the Trigger and Threshold pins together. Now I'm going to mix myself another drink.

Chris

 

[Wayne Meglan]

CDRIVY: I believe you replied to a different post.

 

[CDRIVE]

CDRIVY: I believe you replied to a different post.

It may seem that way because I apparently missed your request for a 6V version of your posted circuit.

That aside try replacing the 12V Zener with a 6.8V Zener like a
1N2804. Then replace the two 1N7003's with a wire jumper.

Chris

 

[Wayne Meglan]

It may seem that way because I apparently missed your request for a 6V version of your posted circuit.

That aside try replacing the 12V Zener with a 6.8V Zener like a
1N2804. Then replace the two 1N7003's with a wire jumper.

Chris

Chris: As I stated in my original post, please excuse my ignorance on circuits. When you say you spiced my circuit, do you mean you modeled it and it didn't work? Thanks for your reply.

 

[Bluejets]

The way the old generator indicator bulb (charge light to some.......ignition light to others) worked was to place it in circuit with the dynomo (D) terminal of the generator ( usually through and ignition switch) and the pos terminal of the battery.
At rest the current would flow from the battery through the lamp and the dynomo winding and light the lamp.

When engine ran, the generator winding would start to charge the battery and the same positive potential was applied to both sides of the lamp and it would go out.

Maybe google along those lines for a schematic of an old generator system under "ignition light".

 

[CDRIVE]

Chris: As I stated in my original post, please excuse my ignorance on circuits. When you say you spiced my circuit, do you mean you modeled it and it didn't work? Thanks for your reply.

Yes I modeled it but your print didn't spec the 12V Zener so I used a 1N2810. The DC analysis produced a curve that indicated that the LED would be completely off when the battery voltage was only 7V!

Zener characteristics can vary greatly over Zeners rated at the same voltage. Some Zeners have sharp knees (when conducting vs when not) while others are very soft. Quite frankly I'm too lazy to search through the hundreds of Zener models in my library to find one with the sharpest knee.

All that aside I think that circuit is not suitable to withstand the environmental variables found on a motorcycle.

I like the simple system posted by Bluejets because it's inherently rugged and won't change a hoot over extreme temperature changes.

Chris

 

[Alec_t]

place it in circuit with the dynomo (D) terminal of the generator ( usually through and ignition switch) and the pos terminal of the battery.

If you don't actually connect it via the ignition switch then you have to find some other way to isolate it until the ignition key is turned: otherwise the battery drains via the D winding of the generator.

 

[Wayne Meglan]

Yes, I will be installing this circuit on the downside of the ignition switch. I did buy a 6.0+ V zener and halved the diodes from the values on the schematic. I put the assembly in a small, plastic box. There are 2 small holes in the back of the box through which the 4 wires leave the box. Three are grounds, one powers the LED. I don't think much water will have a chance to enter the backside of the box through the small holes, but we'll see.

Thanks for all of your help.