Begginer advice needed

[nathanj99]

Hi

I am using the following circuit for a drive coil on a bendini sg wheel. When the drive coil runs the neon comes on to, unless I adjust the variable resister down close to zero. Can anyone explain this to me please?? The rpm of the wheel is much higher when the variable resister is adjusted with the neon lighting.

Thanks

Nathan

[Paul-R]

This is where to find the man himself, but be sure to spell his name properly:

http://www.energyscienceforum.com/activity.php

[nathanj99]

This is where to find the man himself, but be sure to spell his name properly:

http://www.energyscienceforum.com/activity.php

Oh! Yes, I spelt it wrong once and the flipping auto correct now changes the right spelling into the wrong one! Lol

Thanks

[TinselKoala]

When you have the resistor adjusted properly the transistor is switched on and off cleanly and abruptly by the approaching rotor magnet inducing a voltage in the pickup portion of the coil set to turn it on, and this voltage being "quenched" by the opposing field of the second coil as it turns on which then turns the transistor off. This interrupts the current flowing in the larger "secondary" portion of the coil set which is driving the magnet rotor. . When the current in the coil is interrupted its magnetic field tries to collapse. The collapsing field tries to keep the current flowing, but there's nowhere for it to go since the transistor is off. So the voltage builds up until it reaches the threshold voltage of the neon. The neon then fires and becomes essentially a short. This allows the coil's field to collapse more completely because the circuit back to the battery is complete. When the neon turns off the cycle repeats. When you have the base variable resistor turned to too high a resistance the transistor will not turn completely on, so the coil doesn't charge properly and the motor doesn't run as well. When the motor is running well it is flashing the neon so fast that you don't see the individual flashes and it looks like it's continuously lit. If the neon wasn't there, the transistor could fail because the voltage from the collapsing magnetic field could exceed its max C-E voltage rating. This "inductive collapse spike" can easily reach many hundreds of volts so the neon is kind of a safety valve that protects the transistor. The NE-2 neons typically fire at around 90 volts and shut off at around 50-60 volts or so. When they are off they have a very high resistance, essentially open-circuit. When they are on their resistance is very low, essentially a short-circuit. This is why neon pilot lights for AC equipment have to include a current-limiting resistor, so that no more than a few milliamps will flow when the neon is on. Another interesting thing about neons is that only the negative polarity electrode actually glows. If you see both glowing, you know that you are seeing AC, which is alternately making each electrode negative, at the frequency of the AC current.

[topothemtn]

TinselKoala.  That is probably the best explanation of that circuit I have ever read.

Good work.

topothemtn