# Tag Info

5

simulate this circuit – Schematic created using CircuitLab Figure 1. An adjustable potential divider and the fixed equivalent potential divider when the wiper is in the centre position. In both cases the voltage at the bottom is 0 V, at the top it's 5 V and in the middle it's 2.5 V. The difference with the potentiometer is that it's adjustable. Turn ...

3

There are two issues with your schematic. You need a power P-channel MOSFET to switch the power to U4. You can command it with a small N-channel MOSFET (M2) like this: simulate this circuit – Schematic created using CircuitLab When M2 is off, M1 is also off (as R1 pulls its gate to source). R2 keeps M2 off for the brief period when the ATmega starts ...

3

If the "old PSU" is a desktop PC PSU then it's case is almost certainly connected to ground. So yes the case of an old desktop PC PSU could be used as a grounding point. Laptop PSUs on the other hand generally do not have anything accessible connected to mains ground. For ESD protection you DO NOT want a low impedance connection to ground, for two ...

3

This is super simple; It's 12kOhm. Why? The 18kOhm resistor is in parallel with a voltage source, ie. it has NO influence on anything, throw it away.. The 6kOhm resistor is in series with a current source ie. it has NO influence on anything, throw it away.. What are you left with? And so what is the output impedance of your circuit??? To get maximum power ...

1

How do you calculate the power and energy of a signal given only the frequency domain form of the signal function? For power you do it in exactly the same way that you would in the time domain; Time domain: $P(t)=V(t)I(t)$ S-Domain: $\tilde{P}(\omega)=\tilde{V}(\omega)\tilde{I}(\omega)$ If you don't know $\tilde{V}(\omega)$ and \\$ \tilde{I}(\...

1

Yes, the 2W will be cooler, because it's bigger, so has a larger thermal exchange surface with air. If you don't have a 2W 240 ohm resistor in stock you can use four 1kOhm 0.25W resistors in parallel. If you put them in the airflow of the fan they should stay well below finger-burning temperature.

1

There is no inductor energy release problem here! as it will be absorbed by the transformer windings. The problem is that after the short (created by closing the switch) there is no current getting to the input of the bridge rectifier. To solve it just move the switch across the bridge rectifier input terminals and connect a resistor and a capacitor across ...

1

When wiring a prototype PCB, I use bare solid wire to make the connections. I use 24 AWG for most connections. Sometimes I use 20 AWG or 16 AWG for ground and power buses, or high current paths. You can probably use 24 AWG for everything. 24 AWG is a personal preference, you could probably use a slightly smaller wire for your project. For components with ...

1

You can't use an N-channel MOSFET like this, because source voltage will be higher than gate once it opens. You can either use a P-channel MOSFET and reverse the gate logic or put your N-channel MOSFET to a low side (switching the "ground path"). But as we don't know what lies behind the U4 and which type of convertor it is, I'd rather pick ...

1

To power down a whole circuit the logic needs to go something like: Switch feeds a GPIO signal (Sense), and also powers the circuit (through a diode). A power controller (U2) is powered on and activates a Parallel power pathway to the switch (M1). Switch is turned off - Parallel pathway remains active, but Sense is now off since diode prevents Parallel path ...

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