Hi
Quick question,
how does powerpanels convert
12v to 1.2v?? (for the glow start)
is it a potential divider or Bridge Rectifier?
circuit diagrams will be very useful.

(this is for my GSCE DT again)

Thirty years ago when no money existed for better solutions I used a big resistor. I think the value was 2 ohms and 5 watts but that is stretching the memory. The power panels are probably more sophisticated.

A glow plug is designed for 1.5v. There is no memory of ever burning up a plug.

Bill

A potential divider (in the US we call it a voltage divider) or a voltage regulator is used.

A bridge rectifier is used to convert alternating current (AC) to direct current (DC).

Mark

I made mine from scratch ! I used a 680 ohm resistor

A simple way is with a rheostat. A more sophisticated (spell that dollars) would use an adjustable voltage regulator or even a current regulator. Just buy a separate clip on battery of some sort, it's easier.

On modern power panels the glow plug current is controlled by a current regulator IC that has an adjustable pot. There is also a meter on the power panel that shows you what is happening. The power panels also include a reversable switch for your electric fuel pump and connector jacks for your starter. You can plug the 12 volt charger into the starter jacks to recharge your field box battery. That being the case, I would just bite the bullet and buy one. They may look expensive but they do a lot of things and are reliable.

I was thinking of building one last fall. I went to google and within 10 minutes found 3 or 4 designs. I decided it was too much trouble to go track down all the parts so I kept using my 15+ year old power panel.

Power panels do not convert the 12 volts to 1.2 volts. It works by pulse width modulation. It put a 12 volt pulse onto the plug for approximately 1 millisecond, turns it off for 9 milliseconds, back on for 1 millisecond etc. etc. for an average voltage of 1.2 volts. When you turn that pot on the front panel you simply increase or decrease that 1 millisecond pulse a short time to increase the average voltage. If you have a friend with an oscilloscope, he can show you the waveform to verify this. Using a resistor to drop the voltage would be extreemly wasteful of energy and quickly discharge your 12 volt battery. You can find the circuity to build you own on the web at several sources.

Hi!
But how about those automatic powerpanels, how do they work?
Regards!
Jan K
Sweden

Quite well.

Volkan,
Send me a PM and I can send you a diagram with instructions in PDF if you want.

Cheers.

Rodney is correct. The glow plug doesn't care about the voltage, what matters is the heating effect of the current.

The glow driver in a power panel is a current regulator not voltage. By chopping the current electronically the average heating effect is reduced.

Terry

There are lot's of ways to get the job done but they all rely on the same principle.
Ohms Law says that Current = Voltage / Resistance.
Power = Current * Voltage which in this case is pretty much all getting dissipated as heat in the glow plug. But current and voltage are joined at the hip because of Ohms law.
You can do a little algebra and come up with Power = Current^2 * Resistance = Voltage^2 / Resistance

So, that means you can manage voltage or current and still get power to the plug. Some options are:

*You can use a voltage divider to get the voltage and current in a range that won't burn out the plug. That's simple but it does work.

*An analog voltage regulator keeps the voltage part constant. The resistance of the plug changes a bit with its temp but as long as the voltage is high enough, you'll still create enough current and heat to light the plug.

*An analog current regulator will work too. It will automatically adjust source voltage to compensate for any changes in resistance of the load (plug). This allows you to keep the current constant as the plugs resistance increases with temp. That will keep the plug hotter than a voltage regulated source. This is the way that seems to be the best/simplest if you're going to build it yourself. The Ghost posted a schematic for a constant current source that is about the simplest you can make.

*You can also use digital duty cycle regulation techniques like pulse width modulation or pulse frequency modulation like Rodney pointed out. The idea is to average higher current or voltage values over time to get the levels you need. This doesn't work on all types of loads but it will work on a glow plug. I honestly don't know how many panels use this approach but the circuitry is more complicated and expensive than a voltage or current regulator would be.

In the old days people just connected a 1.5V dry cell to the plug. I use a rechargeable glow plug igniter with a 1.2V NiCad. It doesn't regulate current and it doesn't use pulse modulation but it works great.

Mark

Thanks for the help guys,
I think i will do with Ghost's diagram.
I cannot just buy one! this is for my GSCE's!!

I will post the fully diagrams when finished!

Thanks.

Here is what I got so far.
I haven't implemented the volatge reg yet, its on my
todo list.
oh, and Vin will be 12v not 9v
Quite a simple circuit.
LED, BUZZER, and FUEL PUMP CUT-OFF happen only when the tank is being filled
and the float switch is activated (ie, the tank is full [i may replace that with a moisture sensor])

The Pump will never turn off, if you are emtpying the tank.

Comments Welcomed.