elchambro
  • Member for 2 years, 11 months
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Why aren't garage door sensors retroflective on one end?
22 votes

A white card placed in the beam close to the transceiver end will fool the beam. A transmitter-receiver pair across the space to be protected is much more resistant to defeat in this fashion.

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Why isn't there any EEPROM in STM32F4 MCUs?
11 votes

EEPROM is very expensive in terms of cell size (leading to a larger die and hence higher cost). Manufacturers started trying to get rid of EEPROM as soon as the first Flash based controllers were ...

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How can I convert a 4-digit BCD number to Binary in hardware? (using 74LS ICs and GAL22V10 ICs)
5 votes

Since you appear to be happy to user older technology, you could use a 16-bit xPROM (Flash EPROM or EEPROM if you prefer). Feed the BCD into the address lines and take the result from the bottom 10 ...

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What mosfet do I use in induction heater?
4 votes

Two things for you to check. 1) Ensure that the power supply rise time is FAST. Generally don't switch the power supply on with the inverter connected, the inverter can get into a linear mode that ...

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How does a transformer operate with a short in the windings
2 votes

A shorted turn is usually catastrophic for a transformer. Very high currents flow in the shorted turn, leading to further insulation breakdown and dramatic temperature rise. This keeps getting worse ...

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Problem with drawing vector lines on an XY oscilloscope, caused by X and Y being set at slightly different times
2 votes

You could pause at each vertex. This will make the vertices brighter, but you could use the Z axis (beam brightness) to reduce that effect. So: Set X1 Set Y1 Set Z=off Pause Set Z=on Set X2 Set Y2 Set ...

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Wiper Motor Internal Park Switching
2 votes

A SPST switch may be used when the motor is controlled by an Electronic Control Unit (ECU) with two relays - one for Hi/Low and the other for Run/Brake. The SPST switch is read by the controlling ...

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Why the redundant fuse and redundant rectifier diode (series)
Accepted answer
2 votes

The MOVs from each phase to ground slowly degrade with incoming surges and transients and eventually fail short. The fusible resistor protects the unit from damage caused by excess dissipation in the ...

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What are the Pros and Cons Using a Relay to Bypass LAN with Dual Ethernet Ports after POWER LOSS
1 votes

This is a known technique - see for example https://www.win-ent.com/1U-Rackmount-Platforms/pl-80310. My understanding is that it is done right at the RJ45 connectors, rather than at the PHY output. To ...

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Stop a Relay H-Bridge for Brushed DC-Motors to get burned
1 votes

The arc is formed when the moving relay contact moves away from the 24v terminal and draws the arc to the 0v terminal of the relay. So the arc forms from 24V to ground, and can destroy the relay as ...

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Why am I getting 239 VAC between GND and line when the device is turned off?
1 votes

Possible scenario: If the neutral is switched, and in the power supply there is an EMC capacitor between ground and L, the EMC capacitor leakage may be charging the power supply capacitors slowly. ...

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Adapter load switch MOSFET schematic questions
1 votes

In my experience (and I realise this is opinion, so take it with a pinch of salt) reference designs vary widely in their design excellence. Some are clearly the result of comprehensive design, testing ...

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How to power a high current / low voltage circuit through wall outlets?
1 votes

I suspect it's a misprint (or a deliberate mis-specification). Should 1.8W per meter. My reasoning is as follows: For the 5m roll, the connecting wires would not support 18A @5V they are just 1-2A ...

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BTS441RG Chip Failure When Reverse Powered
Accepted answer
1 votes

See Note 13 on Page 7 of the BTS441 Datasheet. You are effectively reverse battery connecting the device. A 150R Ground resistor is required to limit ground current in this case. Additionally, ...

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Simpler ways to develop a buck regulator
1 votes

It appears to be a hysteretic buck regulator. Please see link for more details. Briefly, the switch turns on if the output voltage is lower than the setpoint, and off once the output voltage rises ...

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Soft Touch Lamp Turning on by Itself
1 votes

There's been some detailed analysis of similar problems - for example here Summary - RF energy gets into the switch IC and causes random ON/OFF. The solution is to wire inductors or resistors in ...

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Maximum fuse rating before a MOV (varistor)
1 votes

Commonly, for example in multiple outlet powerboards that include a MOV for surge protection, a thermal fuse is also used. The thermal fuse is in contact with the body of the MOV. When the MOV starts ...

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Contact deterioration, arc forming on high power DC switcher
0 votes

From the datasheet, it looks to be intended for a 24V system. There is a huge difference in switching 24VDC and 48VDC. You need a relay with either: A much larger contact gap, so the arc self ...

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Explanation of a sample circuit for the FL5160 Dimmer controller
0 votes

Operator safety is achieved by using a potentiometer with a plastic shaft, and optionally a special internal construction that guarantees a second layer of insulation. The housing for such a circuit ...

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Help Identifying a chip from a Schlage lock
0 votes

There are a number of LM324 equivalents that include 8524 in the part number. For example NJM8524. Have a look at the pinout and surrounding components on the PCB to see if it looks like a quad op-amp....

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Big capacitor near input power connector
0 votes

In addition to the other answers regarding supply line filtering, the energy storage function of the capacitor also operates if the motor controller is capable of "braking" the motor. In that case, ...

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Can you replace a RJ45 connector with smaller connector?
0 votes

IF you're not interested in following any particular standard, just achieving a smaller connector footprint within a system you have control over, then I suggest using a USB-C connector. With careful ...

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Detecting HI-Z state of charge controller
0 votes

You could try the following configuration. It shows one LED for high, the other LED for low and both LEDs (slightly dimmer) for Hi-Z. Check that your input voltage is enough to turn both LEDs on in ...

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Using enameled copper wire as a capacitor for measuring water level in a tank?
Accepted answer
0 votes

Unfortunately no. Several other good answers address the capacitance problem. Another problem is that the lacquer on enamelled copper wire is not guaranteed pinhole free i.e. the insulation is likely ...

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Can a PTFE coated wire heat up enough to be used as a heating element
-1 votes

Copper has a very low resistance, so it will require a lot of current to dissipate any appreciable power (even 7.5W would need many amps). PTFE covered resistance wire is available, if you are ...

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Why isn't there a non-conducting core wire for high-frequency coil applications
-1 votes

There is indeed a variant on insulated core wire for very high frequency applications. It's called a waveguide. It's a hollow tube used for conducting RF. I am of the understanding that the signal ...

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