inputing to PIC 16F627A from Car wiring

This is the place for any magazine-related discussions that don't fit in any of the column discussion boards below.
Post Reply
JPKNHTP
Posts: 488
Joined: Wed Jun 29, 2005 1:01 am
Location: Missouri
Contact:

inputing to PIC 16F627A from Car wiring

Post by JPKNHTP »

-JPKNHTP
-God Bless
bodgy
Posts: 1044
Joined: Tue Dec 04, 2001 1:01 am
Location: Australia
Contact:

Re: inputing to PIC 16F627A from Car wiring

Post by bodgy »

A couple of things.<p>1. Make sure that the actual power supply to the Pic is as clean as possible, a choke in series in the post regulator stage or using a regulator specially designed for the car environment would help. Also ferrite rings around the power leads at the entry to the power supply would help.<p>2. Resistor in series to each pin used, will help overcurrent problems. Two diodes one with cathode to +v and one with anode to -v in series with each other, so that the cathode junction where the diode with anode to -v meats the anode of the other diode goes to the pic pin and also the signal line. Schottky diodes would be best or a very fast acting diode.<p>3. Enclose in an earthed metal box. Make sure power supply wiring and traces is larger than the other wires. Make sure the earth is a good earth. Twisting the signals wires may help. Possibly though not likely using a feed through diode(used in RF work) may help.<p>4. Real last resort, isolate the signal wires using an opto isolator.<p>One problem may also be the voltage on the MCLR pin is not rising fast enough and you are getting a reset condition. <p>Colin
On a clear disk you can seek forever.
JPKNHTP
Posts: 488
Joined: Wed Jun 29, 2005 1:01 am
Location: Missouri
Contact:

Re: inputing to PIC 16F627A from Car wiring

Post by JPKNHTP »

-JPKNHTP
-God Bless
JPKNHTP
Posts: 488
Joined: Wed Jun 29, 2005 1:01 am
Location: Missouri
Contact:

Re: inputing to PIC 16F627A from Car wiring

Post by JPKNHTP »

-JPKNHTP
-God Bless
User avatar
philba
Posts: 2050
Joined: Tue Nov 30, 2004 1:01 am
Location: Seattle
Contact:

Re: inputing to PIC 16F627A from Car wiring

Post by philba »

The caps are going help filter low frequency ripple - I doubt there is much of that in the car. Noise is another beast and it can get picked up well down stream of your powersupply. I would heed bodgy's suggestions. ferrite beads are your friends here.<p>Also, the signals coming into your PIC - are they 12V? You should use a divider to get them down to 5V if you aren't using opto isolation. <p>You might consider a low pass filter on your signal lines. Since noise often has a fairly high frequency (spikes with fast rise and fall), a well chosen pass frequency that is above your expected signal will help a lot.
JPKNHTP
Posts: 488
Joined: Wed Jun 29, 2005 1:01 am
Location: Missouri
Contact:

inputing to PIC 16F627A from Car wiring

Post by JPKNHTP »

-JPKNHTP
-God Bless
Post Reply

Who is online

Users browsing this forum: Ahrefs [Bot] and 20 guests