Back in the 50s, my dad, who was a college professor at Pasadena City College where he taught electronics, took me into his classroom one Saturday afternoon. In a walk-in closet were all the student projects. There was a conglomerate of batteries with a single flashing Neon bulb at the top. I've always been fascinated with this circuit for my entire life. Thanks.
Yes, the voltage across the cap is a close approximation of a sawtooth wave. There is some slight curvature of the ramp in each "tooth" due to the exponential rise of voltage on the cap. The pk-pk voltage of the wave is typically 20 to 30 V and raised up by DC level of somewhere around 100 V. For this particular lamp, I measured the sawtooth going between 100 V (the lamp's turn-off voltage) and 125 V (the lamp's turn-on voltage). Other lamps will have will have different characteristics.
I recognize those batteries, They were used in vintage vacuum tube radios. I mostly remember the 22 1/2 volt batteries that look similar, but a little larger. Then there was the 57 1/2 volt "B" batteries. And 45 volt batteries. They are long gone and no longer available.
I've been trying to get 9 of these to randomly blink with different capacitors across each NE5 lamp. They all go into a box that someone made back in 1970 or so. I've been knocking myself out over this... they used the same style capacitors that you have there.. All old school. My parents swore that it had been self contained and "on" for a couple years back then, but I haven't been able to figure out a battery combination that would work... but seeing that book and the 50 volt batteries... it is all clear now!! I wish I had seen this video a few months ago..... the project got me playing with IN18 tubes.... those need a little bit more voltage though... and only about 4 milliamps. Thanks for the video! I wish I could reincarnate as an EE.
It is not safe to touch the batteries' terminals at 150V although it seems just to heat a little. The real danger from DC currents is that a lasting discharge can trigger some electrolytic process inside you body and make poisonous substances. In this sense, AC shocks are less dangerous for a given current than DC ones, because the reaction is always being reversed; but with DC, these substances may accumulate and become dangerous to your health.
That flash must last an extremely short time. It would be interesting to put the bulb in a dark chamber with a photoresistor or a phototransistor hooked up to a scope to measure the burst.
This is quite an old video and I'm not sure how quickly I'll get a response but I'm a highschool physics teacher helping a student who is very curious about these circuits. We have been successful in getting a neon bulb to light up with a power supply of batteries and some resistors in series. When we connect a capacitor in parallel with the bulb the bulb stops glowing altogether. The circuit continues to have current leaving the battery and the voltage drop on the capacitor and bulb are constant values. Any idea what's going wrong?
Back in the 50s, my dad, who was a college professor at Pasadena City College where he taught electronics, took me into his classroom one Saturday afternoon. In a walk-in closet were all the student projects. There was a conglomerate of batteries with a single flashing Neon bulb at the top. I've always been fascinated with this circuit for my entire life. Thanks.
just found out how cool neon lamps are... and your video after 11 years lol... good shit :)
Yes, the voltage across the cap is a close approximation of a sawtooth wave. There is some slight curvature of the ramp in each "tooth" due to the exponential rise of voltage on the cap. The pk-pk voltage of the wave is typically 20 to 30 V and raised up by DC level of somewhere around 100 V. For this particular lamp, I measured the sawtooth going between 100 V (the lamp's turn-off voltage) and 125 V (the lamp's turn-on voltage). Other lamps will have will have different characteristics.
I recognize those batteries, They were used in vintage vacuum tube radios. I mostly remember the 22 1/2 volt batteries that look similar, but a little larger. Then there was the 57 1/2 volt "B" batteries. And 45 volt batteries. They are long gone and no longer available.
Thank you so much for this video.
I've been trying to get 9 of these to randomly blink with different capacitors across each NE5 lamp. They all go into a box that someone made back in 1970 or so. I've been knocking myself out over this... they used the same style capacitors that you have there.. All old school. My parents swore that it had been self contained and "on" for a couple years back then, but I haven't been able to figure out a battery combination that would work... but seeing that book and the 50 volt batteries... it is all clear now!! I wish I had seen this video a few months ago..... the project got me playing with IN18 tubes.... those need a little bit more voltage though... and only about 4 milliamps. Thanks for the video! I wish I could reincarnate as an EE.
Given the high DC component, you would need to use an AC coupling cap between the sawtooth generator and whatever circuit it's driving.
It is not safe to touch the batteries' terminals at 150V although it seems just to heat a little. The real danger from DC currents is that a lasting discharge can trigger some electrolytic process inside you body and make poisonous substances. In this sense, AC shocks are less dangerous for a given current than DC ones, because the reaction is always being reversed; but with DC, these substances may accumulate and become dangerous to your health.
That flash must last an extremely short time.
It would be interesting to put the bulb in a dark chamber with a photoresistor or a phototransistor hooked up to a scope to measure the burst.
It depends on the size of the capacitor.
Also, why not just scope the voltage?
This is quite an old video and I'm not sure how quickly I'll get a response but I'm a highschool physics teacher helping a student who is very curious about these circuits. We have been successful in getting a neon bulb to light up with a power supply of batteries and some resistors in series. When we connect a capacitor in parallel with the bulb the bulb stops glowing altogether. The circuit continues to have current leaving the battery and the voltage drop on the capacitor and bulb are constant values. Any idea what's going wrong?
so this is a sawtooth generator?
yes
Can't read the image is not clear.