Searching \ for '[OT] Reed Relay problem for 16C84 based truck ligh' 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=relay
Search entire site for: 'Reed Relay problem for 16C84 based truck ligh'.

Exact match. Not showing close matches.
PICList Thread
'[OT] Reed Relay problem for 16C84 based truck ligh'
1998\01\21@154347 by Bryson, William G (Bill)

flavicon
face
I am using a 16C84 PIC to create a light bar for the 5 marker lamps (Cabover
lights) on top of a Chevrolet Truck. The lights scroll left or right when
that respective blinker is on. They also all blink in sync with the
Emergency Flashers and are all on solid with when the parking lamps are on
(with no blinker or flashers). For the record, I have 3 inputs:  left /
right blinker, and parking lights.

The 5 light outputs from the PIC are input into a 74LS04, Hex Inverter. The
5 outputs of the Hex Inverter drive the coils of 5 Radio Shack 5VDC Reed
Relays (part# 275-232).  The relay contacts are passing 13 to 13.8V to the
lights. The current for each light is about 275ma (.275 Amps).

The problem is the CONTACTS of the reed relays are sticking intermittently.
Any of the 5 contacts may stick. The coil voltage is not the problem. The
contacts may still be stuck after powering down the circuit  and powering
back up without any power to the coil.  I have also shorted the coil while
the contacts are stuck to no avail.

Heat is NOT the problem for the sticky contacts.  The contacts have become
stuck immediately after the entire system had sat for hours. However,
sometimes it is necessary to cool the system for several seconds to unstick
the contacts.

I would appreciate any technical input anyone might be able to provide.

On a lesser note, I have been unable to locate the manufacturer of the
relay. There is an 'OMR' or 'DMR' and a 'DEG' name on the relay. Any ideas
on who and where this company is located.

Thanks....

-------------------------------------------------
Work all day & night,
deliver on time & on budget,       Regards,
and justice for all...             Bill Bryson

1998\01\21@155220 by Andrew Mayo

flavicon
face
See if the contacts stick even when not passing current. I think really
you should use conventional relays, or transistors. Reed relays do tend
to suffer from this problem when switching a load. Remember the lamp
inrush current is much larger than the steady-state current. This is
possibly the reason for the problem. You could possibly alleviate it by
placing a wirewound resistor in parallel with each relay to pass
sufficient current to preheat the lamp filament (it will last longer,
too). Enough current to make the lamp glow very dimly in absolute
darkness is sufficient.

{Quote hidden}

1998\01\21@160423 by ndie Ohtsji [4555]

flavicon
face
Bill,

Did you add any diodes across the relay coil (anode to gnd, cathode to
+12VDC)????   The diode provides path for current to flow once the
12 volts is removed.  Remember the coil is just a big inductor.



+12DC --------+-------+
             |       |
            ---     ---
            /_\     | | Relay coil
             |      ---
             |       |
GND  --------+-------+


Hope this helps!

-Randie
                                   ________
  Randie Ohtsji                   / ____/ /__  ____  ____ ___  _________
  email: rohtsjispamKILLspamglenayre.com    / /___/ / _ \/ __ \/ __ `/ / / / __/ _ \
  Glenayre R & D                / /_\ / /  __/ / / / /_/ / /_/ / / /  __/
  Vancouver, B.C.  CANADA       \____/_/\___/_/ /_/\__,_/\__  /_/  \___/
  Phone: (604) 293-1611 x4555      ________________________/ /
  Fax:   (604) 293-4317           /_________________________/




{Quote hidden}

1998\01\21@162650 by wwl

picon face
On Wed, 21 Jan 1998 14:43:02 -0600, you wrote:

>I am using a 16C84 PIC to create a light bar for the 5 marker lamps (Cabover
>lights) on top of a Chevrolet Truck. The lights scroll left or right when
>that respective blinker is on. They also all blink in sync with the
>Emergency Flashers and are all on solid with when the parking lamps are on
>(with no blinker or flashers). For the record, I have 3 inputs:  left /
>right blinker, and parking lights.
>
>The 5 light outputs from the PIC are input into a 74LS04, Hex Inverter. The
>5 outputs of the Hex Inverter drive the coils of 5 Radio Shack 5VDC Reed
>Relays (part# 275-232).  The relay contacts are passing 13 to 13.8V to the
>lights. The current for each light is about 275ma (.275 Amps).
>
Reed relays are not really designed for load switching. Remember that
the inrush current for a 275mA lamp load may be a lot more due to the
low resistance of the cold filament.
Use Transistors or MOSFETs to switch this kind of load - smaller, more
reliable and probably cheaper as well!
    ____                                                           ____
  _/ L_/  Mike Harrison / White Wing Logic / @spam@wwlKILLspamspamnetcomuk.co.uk  _/ L_/
_/ W_/  Hardware & Software design / PCB Design / Consultancy  _/ W_/
/_W_/  Industrial / Computer Peripherals / Hazardous Area      /_W_/

1998\01\21@162655 by peter
flavicon
face
Bryson, William G (Bill) wrote:

> lights. The current for each light is about 275ma (.275 Amps).

Inrush current will be 4/5 times, this is the probable cause

> The problem is the CONTACTS of the reed relays are sticking intermittently.

> relay. There is an 'OMR' or 'DMR' and a 'DEG' name on the relay. Any ideas
> on who and where this company is located.

OMR ? check out Omron they are a MAJOR relay manufacture



KILLspampeterKILLspamspamcousens.her.forthnet.gr

1998\01\21@162659 by Najemy, Daniel

flavicon
face
One source that we use for reed-relays is as follows:

       Standex Electronics
       4538 Camberwell Rd
       Cincinnati, Ohio 45209

       Phone: (513) 871 3777

The application I've used them in is quite different - we use only 1 or
2 (or sometimes even 1/2) turn around the relay to sense very high
currents in backplanes.

There is some hysterisis associated with the relays, as the primary
force that trip them is driven by electric fields. The fields have to be
gone for a sufficient amount of time before the switch will open.

Reed relays are also subject to close during vibration - this may not be
a good thing if it's on top of your truck.

Is this going into production? or are you just having fun? You may want
to use a mosfet or bjt instead of the relay. A nice p-channel mosfet
would do the job.

Daniel Najemy -  Data General Corporation, Numaliine Power Systems

> {Original Message removed}

1998\01\22@050827 by Geoff Wootton

flavicon
picon face
I had the same problem with just a 150mA inductive load. As Mike Harrison
says, reed relays are not really suitable for load switching. In my case
I used a transistor instead and have had no problems since.

Geoff.

1998\01\22@104314 by Bryson, William G (Bill)

flavicon
face
To all who replied to my request - thanks for the advice...

My problem indeed ended up being in-rush current.  I am in the process of
replacing the reed relays with either transistors or a ULN2803A Darlington.
Thanks to all...

-------------------------------------------------
Work all day & night,
deliver on time & on budget,       Regards,
and justice for all...             Bill Bryson


> {Original Message removed}

More... (looser matching)
- Last day of these posts
- In 1998 , 1999 only
- Today
- New search...