HELP! Circuit power supply problem. SHOWSTOPPER! - Electronic Circuits Projects Diagrams Free

Dangerous · 27th July 2008, 03:09 PM

Hi,

I am using a PIC microprocessor to detect a pulse. I have the MikroBasic code working 100% in an EasyPic5, no issues at all.

The problem is that I am detecting a pulse from a separate circuit, with it's own power supply.

The final version of the circuit will hopefully all be running off the same power supply.

The pulses I am detecting are a 5V signal, so a great TTL source. However, to measure these pulses, I have to measure between this pin and 5V, with 5V connected to the EasyPIC GND.

Obviously I cannot use the 5V line as the signal ground, so what do I do? Do I have to use two power circuits?

I think a picture is now necessary to show what I mean..

(Copy and paste the following into notepad. Use Courier New as the font. Disregard the fullstop's).

............. ________ ...........................
5V --------->|........|................__________
.............|..Test..|................|...Easy..|
GND--------->|.Circuit|................|...PIC5..|
.............|........|................|.........|
.............|........|<5V------------>|...GND...|
.............|........|................|.........|
.............|........|<Pulse Out----->|...RB0...|
.............|________|................|_________|
Please help. I need a low-tech solution, and I need it quick.

House0Fwax · 27th July 2008, 03:21 PM

How about using an optocoupler ?

saturn1bguy · 27th July 2008, 08:41 PM

Quote:

Originally Posted by Dangerous

However, to measure these pulses, I have to measure between this pin and 5V.

Why? What do the output pulses look like referenced its own ground? Perhaps if you posted the schematic of the test circuit (pulse generating circuit) it would shed some more light.

Dangerous · 27th July 2008, 10:43 PM

I don't have a diagram of the test circuit. It is not my product.

If you look at the output pulses referencing it's own ground, there is nothing to see. No pulses. Nada.

blueroomelectronics · 27th July 2008, 11:57 PM

As a previous post mentioned use an optocoupler.

Dangerous · 28th July 2008, 01:08 AM

Thanks everyone. I will be using a 4N35.

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27th July 2008, 03:09 PM	(permalink)
Dangerous	HELP! Circuit power supply problem. SHOWSTOPPER! Hi, I am using a PIC microprocessor to detect a pulse. I have the MikroBasic code working 100% in an EasyPic5, no issues at all. The problem is that I am detecting a pulse from a separate circuit, with it's own power supply. The final version of the circuit will hopefully all be running off the same power supply. The pulses I am detecting are a 5V signal, so a great TTL source. However, to measure these pulses, I have to measure between this pin and 5V, with 5V connected to the EasyPIC GND. Obviously I cannot use the 5V line as the signal ground, so what do I do? Do I have to use two power circuits? I think a picture is now necessary to show what I mean.. (Copy and paste the following into notepad. Use Courier New as the font. Disregard the fullstop's). ............. ________ ........................... 5V --------->\|........\|................__________ .............\|..Test..\|................\|...Easy..\| GND--------->\|.Circuit\|................\|...PIC5..\| .............\|........\|................\|.........\| .............\|........\|<5V------------>\|...GND...\| .............\|........\|................\|.........\| .............\|........\|<Pulse Out----->\|...RB0...\| .............\|________\|................\|_________\| Please help. I need a low-tech solution, and I need it quick.

27th July 2008, 03:21 PM	(permalink)
House0Fwax	How about using an optocoupler ?

27th July 2008, 10:43 PM	(permalink)
Dangerous	I don't have a diagram of the test circuit. It is not my product. If you look at the output pulses referencing it's own ground, there is nothing to see. No pulses. Nada.

27th July 2008, 11:57 PM	(permalink)
blueroomelectronics	As a previous post mentioned use an optocoupler. __________________ Bill Smart Kits build Smart People http://www.blueroomelectronics.com

28th July 2008, 01:08 AM	(permalink)
Dangerous	Thanks everyone. I will be using a 4N35.