Searching \ for ' [EE] Power spikes reseting my pic' in subject line. ()
Make payments with PayPal - it's fast, free and secure! Help us get a faster server
FAQ page: www.piclist.com/techref/microchip/ios.htm?key=spi
Search entire site for: 'Power spikes reseting my pic'.

No exact or substring matches. trying for part
PICList Thread
'[PICLIST] [EE] Power spikes reseting my pic'
2002\02\18@172019 by Daryl Sayers

flavicon
face
I have built a simple watering system using a PIC 1684. Works well on the
test bench but am having problems running live.

I am using a 24V power pack (1A). The 24v is to power the solenoids to
open/close the water valve. I then cut this 24v down to 12v via a 7812
to power the 12 relays that I use to activate the solenoids. I then
use a 7805 to get 5v to power the control circuitry.

My problem is that I seem to be getting spikes (back EMF) into my
control circuitry that is reseting my PIC. I have put a diode across
each solenoid to limit the spike but this doesnt seem to be enough.
I put the diodes inside the box I built. Should I put something
right across the solenoid itself. I was thinking a filter cap. What
sort of cap and what value should I use.



       12v                24v
       |                   |
       |                   |
RA1-4  |\ ULM2803           |
 -----|  \---------+       |
      | /          |       |
      |/           O  -----+
                   O  \
             Relay O   ------+-------------//-------------+
                   |         |                            O
                   |        ---        Long Cable         O solenoid
                   |        /\ Diode   +---//-------------+
                   |        --         |
                   |         |         |
                   |         |         |
           GND ----+---------+---------+


                   12v
                   |
24V     +--------+  |   +--------+    5v to pic etc
--------|  7812  |--+---|  7805  |-------
       +--------+      +--------+    |
            |               |        |
            |               |        |+
            |               |       --- 200uf
            |               |       ---
            |               |        |
            |               |        |
            |               |        |
    GND ----+---------------+--------+

--
Daryl Sayers
Corinthian Engineering                         Ph: (02) 9906 7866
Suite 19, 401 Pacific Hwy                     Fax: (02) 9906 1556
Artarmon, NSW, 2064                         email: spam_OUTdarylTakeThisOuTspamci.com.au
Australia                                     www: http://www.cordoors.com.au

--
http://www.piclist.com hint: The PICList is archived three different
ways.  See http://www.piclist.com/#archives for details.


2002\02\18@172630 by Martin Peach

flavicon
face
I have had this kind of problem and no amount of diodes in any configuration
helped. Finally I shielded the PIC with metal and that did the trick. The
EMF seems to have been radiated inside the box.
/\/\/\/*=Martin

{Original Message removed}

2002\02\18@175149 by Tony Nixon

flavicon
picon face
Daryl Sayers wrote:
>
> I have built a simple watering system using a PIC 1684. Works well on the
> test bench but am having problems running live.



Try putting the diodes on the solenoid terminals.

Bypass the PIC and power supply with 100N caps.

Route the solenoids 24V ground and power seperately from that feeding
the PIC
supply. (ie. star config)

The 2803 chip has common emitter transistors in them, but you show your
connections as high side drivers.

Try placing the relays like this...


12V-----Relay----[2803drv----2803CommonGND]

Pin RA4 may not work as you intended as it is an open collector driver.

--
Best regards

Tony

mICros
http://www.bubblesoftonline.com
.....salesKILLspamspam@spam@bubblesoftonline.com

--
http://www.piclist.com hint: The PICList is archived three different
ways.  See http://www.piclist.com/#archives for details.


2002\02\18@182043 by Frank Waddingham

flavicon
face
Suggest a Diode accross each relay coil (Cathode to +12V) and possibly a
decoupling capacitor say .01mfd as close as possible to PIC VSS & VDD pins.

Daryl Sayers wrote:

{Quote hidden}

--
http://www.piclist.com hint: The PICList is archived three different
ways.  See http://www.piclist.com/#archives for details.


2002\02\18@193411 by Herbert Graf

flavicon
face
My guess is that the power supply is dipping just enough (possibly because
of reflection along the line maybe?) to mess up the PIC. Try putting a small
resistor (say 20 Ohms?) between the 7805 and the 200uF cap, that will
decouple the PIC's supply from everything else. TTYL

> {Original Message removed}

2002\02\19@120126 by Francisco Ares

flavicon
face
I had the oposite, in the bench it did not work and on the final
prototype it did!  I used separate boards, one for the logic and other
for the relays that were activated by NPN transistors

                       +12V
                        |
                        RL
                        |
                        C
logic  >---->>---1KR-----B
signal  conector         E
                        |
                       GND

Francisco


Martin Peach wrote:

>I have had this kind of problem and no amount of diodes in any configuration
>helped. Finally I shielded the PIC with metal and that did the trick. The
>EMF seems to have been radiated inside the box.
>/\/\/\/*=Martin
>
>{Original Message removed}

2002\02\19@121625 by Rick C.

flavicon
face
As a reminder.....ALWAYS put a 0.1uf capacitor on the input of any 78xx regulator
to ground as close to the device as possible. This is in addition to any
electrolytic on the input. You'll be surprised how stable the regulator will be.
Rick

Francisco Ares wrote:

{Quote hidden}

> >{Original Message removed}

2002\02\19@122749 by Martin Peach

flavicon
face
I had separate boards too but the drivers were on the same board as the
logic. I think the problem was coming from the wires that connected the
boards: each relay drive was a separate wire well separated from its
correspondng return wire. If it had been me, I would have twisted each pair
together and bundled the whole lot in a cable.
/\/\/\/*=Martin

{Original Message removed}

2002\02\19@133310 by Paul VanGraafeiland

flavicon
face
It's possible that the spike is being generated by the relay coil itself.

Paul

{Quote hidden}

> >{Original Message removed}

More... (looser matching)
- Last day of these posts
- In 2002 , 2003 only
- Today
- New search...