If there is an essential accessory with heat engines, this is it. The achievement proposed here has been mounted in my field case for several years and has never failed me … until I switch to electric propulsion.
Principle of operation:
The current flowing through T2 (and therefore in the spark plug) is proportional to the voltage on the slider of the potentiometer P1. The transistor T1 is there to help the electrons to pass in T2 and the variable resistance R1 is a protection to avoid passing too much current through the spark plug.
The mounting:
The realization of a circuit is not required (or even no use given the number of component), it can be performed easily on a pelletized circuit or pods in strips. The key is to solder the components well to ensure good electrical contact and good mechanical strength.
The transistor T2 is to be mounted on a radiator to prevent overheating, a single aluminum plate (5 cm x 5 cm and 2-3 mm thick enough).
The galvanometer is however essential. Indeed, it allows to check that the spark plug is not burned out and to adjust the current according to the type of spark plug. An old galvanometer recovered from an old tape recorder or amplifier does the trick.
The shunt is made with some strands of electrical wire previously stripped and untwisted. The number and length of the strands depends on the galvanometer, it must be determined experimentally.
Once the assembly is completed and adjusted, it only remains to fix it permanently in the field case.
The settings:
- To start, the galvanometer is not mounted, the output of the transistor (represented by the arrow on the diagram) is not connected.
- Connect the 12V,
- Ajuster R1 et P1 pour qu’il y ait 6V entre les deux.
- Connect the output of the transistor to ground (0V) through an ammeter (5A rating).
- Adjust R1 to raise the current up to the maximum value that can be supported by a spark plug (I set mine to 3A max. I have never grilled spark plug).
- Mount the galvanometer and the shunt (a few strands). Just adjust the shunt so that the needle of the galvanometer is a maximum for the maximum output current. (Remove strands or increase the length raises the needle).
