Hi all,
I have a 12V solenoid valve (brand U.S. solid, part number USS-PSV00036) that is controlled via a pn2222a transistor with the base connected to Raspberry Pi, as in the circuit below (sol = L1 & R2). The solenoid is a chocolate milk delivery system for a rat. It is connected to some IV tubing on the outlet, squirting milk into a little acrylic feeder, and a syringe with chocolate milk reservoir at the inlet. Concurrently I am measuring small voltages from a rat's brain nearby.
The brain signals are passed through a pre-amp with +/- 5V supply. The supply I am using is a GW Instek gpc-3020 such as the one below. I have it in series configuration with the common tied to earth ground. Left common, left earth ground, and the two commons are not explicitly tied together, if that makes a difference. Current knobs are turned all the way up.
The problem is that I get noise like the image below in my signal when the solenoid operates.
I have tried several configurations of solenoid driver circuitry and grounding connections, including a star ground system, and have not been able to solve my problem. I have also tried several iterations of driver circuitry, swapping the BJT for a mosfet, adding a parallel cap and resistor in between the collector/drain and the solenoid terminal, adding a small resistor between ground and emitter/source.... The noise level is variable, and many times seems worse at the end of a recording session than the beginning. The curious thing is, the only this that seems to reliably get rid of the artifact is to remove the IV tubing from the box where the rat is feeding. In this case, even though the solenoid is still operating and the driver circuitry is the same, and the milk still flows, the artifact disappears. I've tried grounding (to earth and to the Pi ground) the mount of the solenoid and the milk itself, and each time I get voltage transients so bad that my pre-amp saturates and my signal goes poof.
I'm at a loss, any insight that a veteran might have that could begin to point me in the right direction would be much appreciated.
Thank you!
I have a 12V solenoid valve (brand U.S. solid, part number USS-PSV00036) that is controlled via a pn2222a transistor with the base connected to Raspberry Pi, as in the circuit below (sol = L1 & R2). The solenoid is a chocolate milk delivery system for a rat. It is connected to some IV tubing on the outlet, squirting milk into a little acrylic feeder, and a syringe with chocolate milk reservoir at the inlet. Concurrently I am measuring small voltages from a rat's brain nearby.
The brain signals are passed through a pre-amp with +/- 5V supply. The supply I am using is a GW Instek gpc-3020 such as the one below. I have it in series configuration with the common tied to earth ground. Left common, left earth ground, and the two commons are not explicitly tied together, if that makes a difference. Current knobs are turned all the way up.
The problem is that I get noise like the image below in my signal when the solenoid operates.
I have tried several configurations of solenoid driver circuitry and grounding connections, including a star ground system, and have not been able to solve my problem. I have also tried several iterations of driver circuitry, swapping the BJT for a mosfet, adding a parallel cap and resistor in between the collector/drain and the solenoid terminal, adding a small resistor between ground and emitter/source.... The noise level is variable, and many times seems worse at the end of a recording session than the beginning. The curious thing is, the only this that seems to reliably get rid of the artifact is to remove the IV tubing from the box where the rat is feeding. In this case, even though the solenoid is still operating and the driver circuitry is the same, and the milk still flows, the artifact disappears. I've tried grounding (to earth and to the Pi ground) the mount of the solenoid and the milk itself, and each time I get voltage transients so bad that my pre-amp saturates and my signal goes poof.
I'm at a loss, any insight that a veteran might have that could begin to point me in the right direction would be much appreciated.
Thank you!
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