Posts by Olin Lathrop
The reason the transistor is dying is because you didn't put a flyback diode across the relay coil. Relay coils have significant inductance. This means the current can't change instantly without t...
I was hiking around the Berkshires in western Massachusetts yesterday, and came across this metal panel where some power lines were crossing a ridge: The panel is a few meters wide, and appe...
Lower ESR can sometimes be a reason, as you say. However, most of the time the advantage is a wider frequency range over which the combined capacitor has low impedance or low dissipation. The fre...
PCB antennas are not designed by electrical engineers, but guys with pointy hats and wands They use trial and error after starting with the result of some mystic ritual including lots of mumbling ...
Sometimes cables between utility poles make a loop and do a U-turn. What is the purpose of such loops? The loop I'm asking about is in the lower set of wires towards the left of the picture. The...
This sounds like it could be a Paper (https://electrical.codidact.com/categories/35) if written up nicely. It doesn't make sense as a question because you're telling, not asking. I haven't heard ...
Repair questions can be on topic if it's about the underlying electronic principles. Just "How do I fix this?" is off topic. There is little wiggle room for trying to repair a consumer device tha...
Apparently you want to measure the current/voltage relationship of a tunnel diode. The tricky part is that the voltage isn't unique for currents over parts of the range. From your question: No...
Getting into wars about whether something is current controlled or voltage controlled is pointless. In most cases, there is some of both going on. Which "one" to call it then has more to do with ...
Yes, some BOM optimization questions like you mentioned could be on topic. This would include the general techniques for optimizing BOM costs. Getting into specific prices and vendors would be off...
Here is a basic diagram of the power feed to your house, according to what the power company said they found: R1 represents the additional series resistance due to the cable being corroded. R2 re...
It's not totally clear from just the verbal description, but it seems the real question is when/if signal and chassis ground should be connected. If the circuit is not intended to be truly isolated...
Yes, this is safe, but you do have to consider the layout carefully. You have to make sure that nothing conductive gets between the pads of each resistor. For this high voltage safety purpose, you...
No, I have not seen this circuit before, and don't know what source you may have gotten it from. However, I'm not sure that really matters. I don't know what exactly you are trying to teach, but m...
My control system gets a signal representing the plant output, but that signal has a lot of noise on it. The control system goes nuts trying to react to the noise. I need to filter out the noise ...
First, let's redraw the circuit a little more clearly, with logical flow left to right. This also protects the answer from possible changes to the question. As you say, Q1 is a switch to control ...
I'm trying to drive a relay according to a 5 V digital signal, using this circuit: It works for a while, but then the transistor fails. When I replace the transistor, it works for a while again, ...
Roughly around 27 MHz is the old "CB" (Citizen's Band, 11 meter) frequency block. The advantage of this band is that it is free to use with limited power. This is the band "walkie talkies" used t...
First, let's be clear about something. All currents partially take all paths relative to the inverse of the path impedances. It's not an all or nothing function. This "Takes the path of least re...
What the "appropriate" value of R1 is depends on what you are trying to achieve, which you haven't told us. Will this device be used in bright light, like outdoors, and the LED therefore needs to ...
What is a typical value for capacitance of a real inductor? "Typical" capacitance is a useless to design circuits with. It will also vary considerably by inductor size, geometry, and materials us...
Rise and falls times are limited by the maximum slew rate the opamp can produce. This is something you look up in the datasheet. Note that the slew rate might be dependent on supply voltage and p...
In general, the on/off delay is how long it takes from changing the input until the output starts to do something. The rise/fall time is how long it takes to do the something, once it starts doing...
calculate the voltage that will center the magnetic field of a coil This is not possible since the voltage has no effect on the position or shape of the magnetic field. The position and shape are...
That circuit is drawn rather obfuscated, but it does seem to make sense: Start by looking only at D1, D2, C1, and C2. Pretend D3, C3, and D6 don't exist. Although not drawn very well, this is ...
