The way I described winding on the collector winding, then twisting out a tap for Vcc and continuing further turns in the same direction for the base winding, automatically gives the correct phasing.Not a JT builder, but I do know it's easy to get the leads from the 'tickler' coil (the secondary) reversed. If it's not working, try reversing those leads.
What value resistor is that? - I'd put a 15R in series with at least 100R pot and tune for maximum smoke............er - LED brightness.Oh, do I need to wind the secondary coil around the primary one? I probably didn't wind my inductor correctly.
1kΩ - I tried to replicate @DickCappels' flooring nail inductor as closely as possible, but he needed a capacitor to make it work and I don't have one with a small enough value.What value resistor is that? - I'd put a 15R in series with at least 100R pot and tune for maximum smoke............er - LED brightness.
I can't tell if the LED is oriented correctly. I can't tell what the transistory leads are. And I think the coil secondary still might be connected backwards.I did have the battery wired wrong. (I had it wired correctly at first, but changed it when I was trying things out.) Here's my updated circuit:
View attachment 89145
I added many more turns and tried using a different transistor and LED, but the output voltage (measured at the LED) is 0.02V less than the input voltage (measured at the battery). What in the world is going on here?If one winding is in the wrong direction, just swap the two wires to correct the phase relationship.
You might need a whole lot of turns to get this thing working -the one I made had 60 turns collector winding and 60 turns base winding. A small capacitor like 1000 pf or more across the base resistor sometimes helps.
The left end of the inductor is wired to the resistor.(From the photograph, I can't tell what the left end of the long inductor is connected to.)
Consider this: The center tap and the collector are connected by a copper wire (the collector winding). As such, the average (DC) voltage at the collector contact should be almost the same as that on tap. The "magic" occurs when the peak voltage on the collector exceeds the DC on the tap (though the average voltage is the same) and the peak voltage is that which can drive the LED. Is you LED lighting up?
Is the base winding at the opposite end of the coil from the collector winding?
It appears to connect to the battery "-" terminal, and continues as the secondary, as in an auto-transformer. I've looked at the coil, and it appears to me to be connected correctly. Assuming everything else is connected correctly, the problem is, IMO, the transistor isn't biased into conduction, and collector current is zero, meaning the transformer isn't doing anything. I've suggested a remedy, but the TS has decided to ignore the suggestion.(From the photograph, I can't tell what the left end of the long inductor is connected to.)
The blocking oscillator JT works best with nothing more complicated than a current limiting resistor in series with the base winding. Getting above the threshold gets mathematical if you use a voltage divider.One more thing. Your transistor needs to be just above threasold for your JT to work. So, get a variable resistor, say 10K. Connect the ends to VCC and ground, and the wiper to you transistor base, the same point where your coil connects. Power up and slowly turn up the base voltage until your JT magically springs to life.
Course, check all those other things mentioned first.
Not really. Use a 10k pot and slowly turn up the voltage. No math required. Though your comment about a limiting fixed resistor is good. Don't want to burn up the transistor while turning up the voltage. a 1K fixed resistor should limit base current to a safe value.Getting above the threshold gets mathematical if you use a voltage divider.
Sorry, I don't understand what you mean. Could you please explain?Right now, making the oscillator the best it can be is secondary to just getting it to work. Given the components used so far, and the lack of success, quickly implementing a starting circuit would go a long way towards making a working device.