Could not get the circuit to oscillate. Could you give us an idea of the magnitude of the Rsense and Rseries resisters. Also so confirm the accuracy of the circuit diagram, seems strange for an astable oscillator.
@circuitdog This is an unusual circuit because the timing network operates in current mode rather than voltage mode. The component values depend on the characteristics of the inductor. As with an RC timing network, the voltage on pins 2 and 6 must be able to reach 2/3Vcc with pin 3 high. For example if Rsense =1K, Rcoil + Rseries must be less than 500 ohms. It should oscillate under these conditions. Rsense can be adjusted to optimize the sensitivity, since it sets the peak field in the core
Wow, that is much simpler version than classical fluxgate magnetometer. I will put that one on my 'to do' list.
I hope it is sensitive enough to detect disturbance in earth's magnetic field due to solar activity, so that I can make aurora borealis warning system - not to miss any aurora borealis display again in next year or two (2012/2013).
I neglected to show that the frequency will go DOWN when a field of opposite polarity is applied. In that situation the external field subtracts from the field of the coil and causes the core to saturate later, which makes the current waveform rise more slowly. When the frequency is being reduced, a point is reached where the external field completely cancels the average coil field, and the frequency will begin to rise again. Care must be taken if this circuit is used in a feedback loop
Could not get the circuit to oscillate. Could you give us an idea of the magnitude of the Rsense and Rseries resisters. Also so confirm the accuracy of the circuit diagram, seems strange for an astable oscillator.
circuitdog 1 day ago
@circuitdog This is an unusual circuit because the timing network operates in current mode rather than voltage mode. The component values depend on the characteristics of the inductor. As with an RC timing network, the voltage on pins 2 and 6 must be able to reach 2/3Vcc with pin 3 high. For example if Rsense =1K, Rcoil + Rseries must be less than 500 ohms. It should oscillate under these conditions. Rsense can be adjusted to optimize the sensitivity, since it sets the peak field in the core
blackcreekresearch 1 day ago
Wow, that is much simpler version than classical fluxgate magnetometer. I will put that one on my 'to do' list.
I hope it is sensitive enough to detect disturbance in earth's magnetic field due to solar activity, so that I can make aurora borealis warning system - not to miss any aurora borealis display again in next year or two (2012/2013).
Thank you for sharing it with us.
MilanKarakas 6 months ago
So this uses a saturable reactor as the sensor. I've never really understood how these things work though.
douro20 10 months ago
spiffy!
uniment 11 months ago
I neglected to show that the frequency will go DOWN when a field of opposite polarity is applied. In that situation the external field subtracts from the field of the coil and causes the core to saturate later, which makes the current waveform rise more slowly. When the frequency is being reduced, a point is reached where the external field completely cancels the average coil field, and the frequency will begin to rise again. Care must be taken if this circuit is used in a feedback loop
blackcreekresearch 1 year ago
not bad for utility
sonicase 1 year ago