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These "digital relay" modules are available in 3.3V and 5V versions. Simply buy one of the 3V models. Here is one, for example: https://www.dfrobot.com/product-1572.html


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Assuming a relay module: check if it is OK to drive it with 3.3V logic when it is on a 5V power supply, or show the specs for us to look at. Driving a relay module with 3.3V logic is unlikely to harm the ESP32, but it may not drive the relay properly if the relay module expects 5V logic. Generally, I would even prefer using an external power supply rather ...


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Good Job, you are right on, the transistor is rated at 200 mA which is adequate for the job. The flyback diode will protect your system and the transistor. the drain source drop would be maybe 0.01V on a bad day depending on the RDSon. You will probably need a little lower value base resistor depending on the gain of your transistor. I would use something ...


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According to the datasheet there are multiple models. Some already have an input resistor for the led (in the opto-isolator) inside the package, but some don't. For the ones that don't have a resistor inside, you'd need to add one yourself, to limit the current to around 10mA. Some models also have a snubber circuit inside the package. The need for this ...


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If the coil is 70 ohms and it's driven by 5V, it should draw about 5/70 = 71 mA. That's pushing the 2n3904 a bit hard, and doesn't even account for inductive effects. (It's a small-signal transistor.) Do you have an NPN power transistor to try, just as a test? If its current gain (beta) is too low, use a Darlington configuration by combining it with your ...


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The answer is a qualified yes. In this case the relay is optically isolated from the load so there is no cross conduction. You need to connect the relay to the Arduino power +5 and Ground supply. I would not connect more then one to any arduino pin as the relay has a max requirement of 20mA. Not all SS relays are the same so you need to check there specs if ...


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These random values could be nothing but noise as your receiver may be sensing other source of ultra sound. In your case, the circuit is especially sensitive as the output powers a relay and any noise in the input side will cause the relay to "chatter". There are many approaches to filtering and smoothing out the signal. One method would be to ...


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Although your solution would work, it seems open to problems such as missed clicks, starting at a different place etc. A better, more robust and error free solution might be to use a hall sensor. Essentially what a hall sensor does is close a switch when a megnetic force is applied. So all you have to do is add a magnet to your conveyor/chain. This way, you ...


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