PIC10F200 input pin to detect 200V?

[grizedale]

Hello,



We have a signal which is 200V or 0V , and we understand that we cannot simply put that into a PIC pin to detect a logic high.



However, if we put a big enough resistor in series with the 200V, then surely we can simply connect the other side of this resistor to the PIC pin, and all that will happen is that the pin's ESD diode will be forward biased, and the PIC pin (working as an input) will be able to detect it as a logic high?



(We cannot change the PIC circuit as its an already-being-sold sold product.)

 

[milind.a.kulkarni]

Ideally speaking it should..... but remember one thing when you say 0 to 200v supply both of then need a common ground reference...... I am assuming you are saying me the DC voltage of range 0 to 200V

Good Luck

 

[Tahmid]

Yes, you can use it like that. In fact many circuits detect zero-crossing like that (with mains AC).

The current should be very very low. A resistor with resistance between 100kΩ and 2MΩ should be okay to use.

As milind has already stated, the two must have a common reference. If the signal you mention that varies between 200V and 0V is DC, then this and the microcontroller circuit should have the same ground.

Hope this helps.
Tahmid.

 

[LightDiodeDesigns]

I must admit I'd use "opto isolation" at this point, to save any chance of 200v-ing the PIC....
There are quite a few, but basically the 200v flashes an LED (with lots of resistance) that switches (5v) current to the PIC pin....
There are lots of ways, but I like this one
https://uk.farnell.com/fairchild-se...r-dip-8-error-amp-smd/dp/2083067?in_merch=New Products&in_merch=Featured New Products&MER=i-9b10-00001144
Cool :-D
NEAL

 

[bigdogguru]

The following appnotes discusses a similar technique for the implementation of a zero crossing circuit:

PICDIM Lamp Dimmer for the PIC12C508

Interfacing to AC Power Lines

Although it should be mentioned, the lack of any isolation can be extremely hazardous not only to the PIC, but anyone coming in contact with particular parts of the design.

BigDog

 

[betwixt]

With 200V to play with, you could even use a neon lamp and LDR as an opto-isolator. It might cost less than a normal opto-isolator and would certainly work with lower input current than an LED based device. It's reaction speed might be a problem but that would depend on your application.

Brian.

 

[LightDiodeDesigns]

I like it! Or a really-quick-little-steam piston and peltzer pump (on 20nm silicon die) and a reed switch!

Agreed, keep the mains at distance, easiest through light-based switching, which can be fairly (unquantified, sorry) rapid when in use I've found..

Cool, thanx
Neal