Subject: From: Date:

Re: [ECS] micro-redac and relays Dan Carrington Fri, 01 Jan 1999 17:14:59 -0800

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	Mark S., I am sort of catching up on my e-mail and slightly remember
this question going by.  Are you the one trying to monitor a piece of
equipment that has a switched AC socket on the back by putting a
transformer on it and sensing the voltage from the transformer with the
Redac?  The way I do it is how Applied Digital shows on their schematic
page of wiring the Redac.  Hook a 9 volt REGULATED!!! transformer on the
redac.  Negative to pins 9&10 with a small fuse.  Then use dry contacts
to send the positive to the different inputs.  Mine sense instantly that
way without any resistors.  The regulated transformer keeps the voltage
even without any real voltage draw.  Realize that most wall warts are
not regulated and put out many volts more than stated if no current is
drawn.  This can be a problem and can blow things not made for the extra
voltage.  Possibly your problem is your supply has a capacitor in it and
is holding power for a time because the redac is not really using any
current, just sensing voltage.  
	At your piece of equipment, just hook a transformer to the switched AC
and wire it to a relay.  Now switch the regulated 9 volt with the
relay.  You will keep your systems separate, as in no possible chance of
shocks and static into your expensive redac from your monitored
equipment.  Now, you only need one regulated power supply this way and
you can use switches anywhere to sense anything with the redac and it's
local 9v regulated power.  A relay just acts as a powered switch.  

	As a side note, remember to put a diode across the relay's coil,
opposite the regular direction of power to work as a feedback short so
when the relay clicks off, it will not spike power backwards towards
your monitored equipment.

	As a secondary side note, the Redac wiring diagram shows the analogs as
pin #9 having +5 volts and you then resist it back to the inputs 1-8. 
And the relay commons are pins 9 & 10 both.  The diagram shows using a
24v AC transformer through them to secondary high power relays for
controlling things with dry contacts that can handle more power and be
separately powered, not commoned.

Hope this helps...

Dan Carrington





Mark Sekelsky wrote:
> 
> David,
> 
> Thanks for the resistor lesson.  The 2.2 didn't work but the 1K sort of
> does.  With only a fuse in place there is about a 3-4" delay before the item
> state changes to HIGH.  I assume this is residual power in the transformer.
> With the 1K resistor in place that delay is 8-9" but it does change to HIGH
> 100% of the time.  I can certainly live with this but wonder if it means I
> should be trying yet another resistor or not.
> 
> Happy New Year!
> 
> Mark S
> 
> -----Original Message-----
> From: David Mccoll [mailto:dmccoll@intergate.bc.ca]
> Sent: Wednesday, December 30, 1998 4:13 PM
> To: ecs-list@netbloc.com
> Subject: Re: [ECS] micro-redac and relays
> 
> Mark S
> Your connections sound correct. Get it to work 100% before you add the fuse
> and resistor. If the 10K resistor gives you trouble move down to a 4700 that
> is a Yellow, Violet, Red, Gold. If that does not work then move down to a
> 2.2K or 2200 which would be Red, Red, Red, Gold. If that does not work then
> go to a 1K or 1000 which is Brown, Black, Red, Gold.
> 
> Originally you said the power pak was 5V DC 150mA. What are you using now ?
> 
> Here is some gunk on resistors. This is very simple stuff but on the surface
> it may look complicated. The Gold band is what is referred to as the
> "tolerance" of the resistor and is usually the last band.
> 
> Gold is 5% -- most common tolerance
> Silver is 10% -- not too common
> 
> The first 3 bands are the value.  Here is the way I learned to calculate it.
> Bad  ---  Black -- 0  -- .0
> Boys  --- Brown -- 1 -- 0
> Rape --- Red -- 2 -- 00
> Our  --- Orange -- 3 -- 000
> Young --- Yellow -- 4 -- 0000
> Girls --- Green -- 5 -- 00000
> But  --- Blue -- 6 -- 000000
> Violet ---- Violet -- 7 --0000000
> Goes --- Gray -- 8 -- 00000000
> Without  -- White -- 9 -- 000000000
> 
> The first 2 bands are the value and the third band is the multiplier which
> is the number of 0's to add after the value. So 4.7 K.Ohms = 4700 Ohms =
> Yellow, Violet, Red and Gold for the 5% tolerance. The 10KOhm resistor would
> be Brown, Black and Orange the multiplier is usually assumed to be 5% Gold.
> A 100 Ohm resistor is Brown Black Brown and a 10 Ohm is Brown,Black, Black
> 
> Keep up the good work.
> 
> DAvid M

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