Hi Everyone.
I'm doing a little ultrasonic proximity sensor project using components/materials that I have lying around. Attached is the schematic for the ultrasonic receiver amplifier which will be connected to the ADC of a micro.
It all functions properly. The micro sends about 10 cycles (of 40kHz) through a transmitter and the receiver section amplifies and detects the envelope ready for the micro to analyse. (The output is currently disconnected from the micro.)
So far so good. At first, I had it prototyped on breadboard to check the design with the actual transducers. Everything still functioned but my mobile phone rang and I was reminded about EMC as the output started to jump about!
I thought it would be interesting to see at what point the design would become immune to RF radiation from my mobile phone.
So now I have the circuit on stripboard! But I have laid out everything with the tracks AND components on top. I trimmed the pins of everything so that they don't poke through the board. Also, I have cut out a piece of copper-clad board (slightly larger than the stripboard outline) and stuck it under the stripboard as a ground plane.
All connections to 0V are now made via holes drilled to the unspoiled copper plane below.
Immunity is a LOT better. With my phone in front of the transducers there is no interference at all. With my phone above the components, the op-amps are still affected.
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ALL your thoughts on the following points would be very interesting:
1. Is it possible to make the circuit immune using through-hole components on a 2-sided board (WITHOUT sheilding!)?
2. Can it even be made immune with such an old bipolar, leaded op-amp in the design?
3. Is there anything you would do to improve the circuit design to make it more immune, whilst still using an LM324?
I look forward to your opinions very much.
Regards!
I'm doing a little ultrasonic proximity sensor project using components/materials that I have lying around. Attached is the schematic for the ultrasonic receiver amplifier which will be connected to the ADC of a micro.
It all functions properly. The micro sends about 10 cycles (of 40kHz) through a transmitter and the receiver section amplifies and detects the envelope ready for the micro to analyse. (The output is currently disconnected from the micro.)
So far so good. At first, I had it prototyped on breadboard to check the design with the actual transducers. Everything still functioned but my mobile phone rang and I was reminded about EMC as the output started to jump about!
I thought it would be interesting to see at what point the design would become immune to RF radiation from my mobile phone.
So now I have the circuit on stripboard! But I have laid out everything with the tracks AND components on top. I trimmed the pins of everything so that they don't poke through the board. Also, I have cut out a piece of copper-clad board (slightly larger than the stripboard outline) and stuck it under the stripboard as a ground plane.
All connections to 0V are now made via holes drilled to the unspoiled copper plane below.
Immunity is a LOT better. With my phone in front of the transducers there is no interference at all. With my phone above the components, the op-amps are still affected.
---------------------------------------------------------------------
ALL your thoughts on the following points would be very interesting:
1. Is it possible to make the circuit immune using through-hole components on a 2-sided board (WITHOUT sheilding!)?
2. Can it even be made immune with such an old bipolar, leaded op-amp in the design?
3. Is there anything you would do to improve the circuit design to make it more immune, whilst still using an LM324?
I look forward to your opinions very much.
Regards!
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