- Mon Aug 15, 2016 9:15 am
#191269
I am new to working on PCBs and so far the logic is very enjoyable. However, after a few trivial board designs I'm facing a challenge that must be very simple (I'm making a mountain out of a molehill). I'm trying to perform some logic in between 2 existing components. The first component is a circuit board which supplies 24VDC to the second component, a 24VDC PNP photoelectric sensor.
I want to invert the signal and perform a specified delay on the sensor. The delay is fairly straightforward using a delay line from DigiKey. The inverted signal is fairly straightforward as well. My problem is that I am using a 78 series voltage regulator to bring the 24VDC down to 5VDC for the delay circuit and inversion. After the delay, I have a 32mA 5VDC inverted signal. I need to provide 24VDC 100mA back to the circuit board. I am not sure how to get the voltage back up to 24VDC, and at the higher current. I originally considered driving a solid state relay, but the MTBF of a SSR is too small, and the component will fail too frequently. I am now considering a DC-DC converter (link below), which is powered by a transistor whose base is connected to the delay, and emitter is connected to another 78 series voltage regulator 5VDC.
http://www.digikey.com/scripts/DkSearch ... 5720586917
My questions are:
1) The circuit boards in I normally see are almost always operated using 12VDC or 24VDC power supplies, but I know that most circuit board components operate at 3-5VDC. I MUST be missing something obvious. How do I get back to 24VDC output from the board? I.E. - How do current circuit boards input and output 24VDC but perform logic at 5VDC? What component or circuit is common practice?
2) If there is no circuit that I'm missing, will my design work?
Even a quick response of the component I SHOULD be using, or a board layout that performs the task would be greatly appreciated. A small amount of guidance and I will gladly spend the time researching appropriate usage.
Thanks,
Dan J
I want to invert the signal and perform a specified delay on the sensor. The delay is fairly straightforward using a delay line from DigiKey. The inverted signal is fairly straightforward as well. My problem is that I am using a 78 series voltage regulator to bring the 24VDC down to 5VDC for the delay circuit and inversion. After the delay, I have a 32mA 5VDC inverted signal. I need to provide 24VDC 100mA back to the circuit board. I am not sure how to get the voltage back up to 24VDC, and at the higher current. I originally considered driving a solid state relay, but the MTBF of a SSR is too small, and the component will fail too frequently. I am now considering a DC-DC converter (link below), which is powered by a transistor whose base is connected to the delay, and emitter is connected to another 78 series voltage regulator 5VDC.
http://www.digikey.com/scripts/DkSearch ... 5720586917
My questions are:
1) The circuit boards in I normally see are almost always operated using 12VDC or 24VDC power supplies, but I know that most circuit board components operate at 3-5VDC. I MUST be missing something obvious. How do I get back to 24VDC output from the board? I.E. - How do current circuit boards input and output 24VDC but perform logic at 5VDC? What component or circuit is common practice?
2) If there is no circuit that I'm missing, will my design work?
Even a quick response of the component I SHOULD be using, or a board layout that performs the task would be greatly appreciated. A small amount of guidance and I will gladly spend the time researching appropriate usage.
Thanks,
Dan J