# Tag Info

### Why does my voltage divider output seem to vary depending on the order of magnitude of overall resistance?

Since the analog pins use a sample and hold circuit firstly I wouldn't use as large as possible resistors to get the buffer effect(drawing minimal current) that you mentioned. They form filter ...

### Simple circuit to interface MCU digital input with external high voltage

Here's a circuit that I've used in the past. The key issue is that in a motor vehicle, the electrical system can experience "load dumps" that can create ±200 V transients. simulate this ...
• 177k
Accepted

### Simple circuit to interface MCU digital input with external high voltage

The 1MΩ resistance seems unnecessarily high - when the ignition is on there will be substantial draw from other stuff, and when it is off there will be zero draw. You're also dividing down the voltage,...
1 vote

### Easiest way to power a 3.3V microcontroller from a 9V input?

You wouldn't usually use zener diodes for a task like this, nor would you use them in series. Zener diodes are used for voltage clamping and they're not particularly suitable for regulation outside ...
• 10.9k

### Easiest way to power a 3.3V microcontroller from a 9V input?

Drop-in three terminal voltage regulator? Probably would go with switching since they generally don't require the input and output filtering caps of a linear regulator and heat dissipation will not be ...
• 21.3k
1 vote
Accepted

### Why am I getting weird voltage amplification with a membrane potentiometer?

It appears that if you take pressure off the 'pot' the 'wiper' goes open-circuit, like a resistive touchpad. So, in the case of your particular input, there's probably some bias current flowing out of ...
1 vote

### How to adjust this circuit to allow measuring of negative voltage beside positive voltage through microcontroller?

Your circuit already can read -18 V to +18 V. With the component values shown, this gives you 0.249 V to 4.732 V at the input of the ADC. You just need to do the appropriate math to convert the ADC ...
• 177k

### How to adjust this circuit to allow measuring of negative voltage beside positive voltage through microcontroller?

If the 18V is isolated from ADC supply you can shift the signal to Adc/2 using tl431. (Working with Ac and Dc input signal also). If not isolated, you can shift with DC blocking capacitor (if it is ...
• 2,320
1 vote

### How to find Resistor value form voltage drop?

You'll no doubt get simpler answers than this, but I wanted to show you all the details of the solution. The long, formal answer, is that we have three laws which together to describe the state of the ...
• 42.2k
1 vote

### How to find Resistor value form voltage drop?

It is very easy to calculate the R values based on the current that you want to have in the LED. R = Vdrop/ ILED. Do also consider a case where the diode could be faulty and is high impedance. You ...
• 4,192