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PCB specs, Meaning of “6-1” diameter

I’m using a relay for a PCB, but have trouble understanding some of the specs for the recommended hole drill sizes. As shown below, the spec sheet indicates a "6-1" diameter hole. What is the meaning of this 6-1? It should be something with a diameter of less than 2.22 mm, but it would be […]

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LiFepo4 RV battery bank, charge from beefy alternator setup

What I’ve got 5x, 200Ah LiFepo4 batteries in a 12V, parallel bank. I’m looking at putting in a Sinister Diesel 320A alternator to supply loads of juice to the battery bank. If this is even possible, without damaging the batteries and circuit, then I figure I don’t really need to go the standard roof, solar […]

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Weird output from MAX3232

Hi – I’m getting unexpected output from a MAX3232 board. I’m trying to reimplement a baseball scoreboard controller. The signal I’m trying to recreate is at RS232 levels (-5 to 5V) but uses a different encoding. I’ve got a Raspberry Pi Zero driving a 3V GPIO (the blue trace), and the output is hooked up […]

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Can’t enumerate USB with STM32F44RE

I am trying to setup USB communication with an STM32F446RE It is a custom board where: The clock source is an external 8Mhz quartz There is a micro USB port with USB+ connected to PA12 and USB- connected to PA11 The external quartz is working (I can load a firmware that just blinks a led) […]

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Magnetic pickup speed sensor

I am looking at a magnetic pickup sensor datasheet. This graph shows the output voltage against the surface speed. However, there are 3 curves, that changes the output voltage range changes. What could be the meaning of "8P", "10P" and "16P"? Are these the poles of the reluctor? There are no other information in the […]

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How much current should a car draw from a battery when it is off?

My SUV died last night, and it draws 540mA now, when the car is off, and nothing (that I know of) is on. How much does a car typically draw from the battery when it is off? EDIT 1: I think you’ve already answered my question (half an amp is an unreasonable amount of power […]

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Frequency of signal

I have a signal like \$\sin(2t)\$. The frequency of this signal is \$f=\frac{1}{\pi}\$, but I am confused here because this \$\pi\$ equals 3.14 or 180 degrees if the signal is \$\sin(2\pi t)\$, then \$f=1\$ and everything is clear. Please tell me what is the difference between them?

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How much current should a car draw from a battery when it is off?

My SUV died last night, and it draws 540mA now, when the car is off, and nothing (that I know of) is on. How much does a car typically draw from the battery when it is off? EDIT 1: I think you’ve already answered my question (half an amp is an unreasonable amount of power […]

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Protecting PC parallel port interface when controlling external devices

I need to control two devices with the PC’s parallel port simultaneously. To protect the port and provide some sort of a buffering, I thought to use an optocouplers and two ULN2003 Darlington arrays. I wonder whether this design is reasonable. Maybe one ULN2003 could be enough in this situation? Alternatively, is there a simple […]

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What ESP32 UART Auto-Program Circuit Alternatives are there?

I am currently designing a board centered around the ESP32. I want to implement an auto-program circuit for convenience’s sake, because I don’t want to hold a boot button each time I want to program it. My question is: Why is the below circuit that most ESPs use, designed the way it is? I am […]