Remote switching question

jbxx · Post by **jbxx** » Thu Jun 10, 2004 4:51 am

Hmmm, I had an idea last night after sombody nearly
got injured at work yesterday.
What I want to do is switch a 20 A. outlet
remotely by radio ( no power available at the transmitting end).
I was thinking along the lines of FRS radios.
About no more than 1000' distance, but possibly between
floors. Maybe triggering an SCR to a relay to handle the current load . DTMF ? CTCSS ? DIG ? Any Ideas?
J.B. AD6WX

motor59 · Post by **motor59** » Thu Jun 10, 2004 5:16 am

My first thought-

If this is safety related, do you really want to depend on a system where some 13 year old with a ratshack FRS toy might accidently re-energize the circuit?

If, however - you put the rx radio on the same circuit you're de-energizing, then it would only work as a disabling device. You'd have to manually reset it to get power back to the rx radio.

Of course, you'd have to be willing to accept that some interference or spurious transmission could cut power on that circuit at any time...

RKG · Post by **RKG** » Thu Jun 10, 2004 8:12 am

Take a look at the PLC (or "X10") line of products available from such sources as SmartHome.com.

A 20A relay is easy to acquire. In basic form, it is switched by PLC commands over the power line, but you can get devices that will send commands over the air (very short distance) to a receiver that will convert them and then send them over the power line.

Alternatively, you can get "transponder" boards that will listen to DTMF commands and use them to open or close low current relays. You could feed the "transponder" audio from a regular radio receiver. You then used the contact closure of the transponder to trigger an X10 command to be send to the PLC 20A switch via an inexpensive module. Range is now a function of how good your radio equipment is.

I do agree with M59 that you should wire an additonal switch in series with the load, so that the circuit can be locally de-powered in a way that cannot be negated by the OTA commands. That switch could be piloted, so that when the red light is glowing, everyone knows that the device in question can be cycled by someone who is not in sight and may not be on the team.

jbxx · Post by **jbxx** » Thu Jun 10, 2004 6:18 pm

I should clarify the application in mind.
I want tobe able to kill a fully loaded 20A circuit.
I was experimenting today by remotely faulting
a GFI with an SCR, works well.
I want to kill a wire pulling machine.
The operator of the machine can not hear anything.
Im talking about pulling say 4 -750 McM in over 1000'
runs . When I want the machine to stop, it needs to stop,
NOW. I want it to be manually reset.
I tried the X10 stuff, but it doesn't have the range.
Over 25 years of pulling big stuff I probably have had
at least a dozen pull failures . Like 10' reels falling off reel
jacks and such, I nearly had my arm sucked into a 6"
conduit one time when a wire surged. We tried to stop the pull,
but as usual, no luck.
J.B. AD6WX ( also known as three fingered J.B.)

kf4sqb · Post by **kf4sqb** » Sat Jun 12, 2004 4:57 am

Interesting problem, JB. What kind of wire puller are you useing? I used to work for an electrical contractor, and have been on several pulls where we used the Greenlee puller. Tough little machine. Believe it or not, we have managed to bog them down before. Then again, we have also had them break concrete when they started pulling out the anchors that we had it attached to the floor with.......! If you can make this work, make it portable, and sell it!

jbxx · Post by **jbxx** » Sun Jun 13, 2004 4:01 pm

I own a few pullers/ tuggers. A couple of Greenlees
an Einsley and a supertugger. I have destroyed all
sorts of equipment with the Greenlees but the
supertugger is about a Greenlee X 10.
The Greenlees could not pull 4-750 MCM over 1000'.
J.B. AD6WX

spareparts · Post by **spareparts** » Sun Jun 13, 2004 6:00 pm

JB,
Consider this - Set it up failsafe. To run, you need the receiver to see the carrier & DPL code. It looses the signal, it drops out the control voltage.

This way if the electronics take a dump, the puller stops & you know your safety system is off line or out of range.

Just a thought-

Martin

thebigphish · Post by **thebigphish** » Sun Jun 13, 2004 9:16 pm

spareparts wrote:JB,
Consider this - Set it up failsafe. To run, you need the receiver to see the carrier & DPL code. It looses the signal, it drops out the control voltage.

This way if the electronics take a dump, the puller stops & you know your safety system is off line or out of range.

Just a thought-

Martin

good idea, a failsafe w/ manual reset seems to minimize the abberant kid with a ratshack FRS from costing you a limb...

OX · Post by OX » Mon Jun 14, 2004 2:45 am

Have your safety officer consult the OSHA code before implementing anything. You would really hate to have something happen with your contraption in the middle of things and OSHA to start asking questions...

jbxx · Post by **jbxx** » Mon Jun 14, 2004 6:19 pm

Safety officer??
Bwahhahahha.
Quite seriously though, all this will do at the worst
is shut the machine down. No possible harm done.
Quite frankly when you are dealing with somthing that has this much power. You don't rely on any safety devices.
Besides at this point there aren't any.
J.B. AD6WX

thebigphish · Post by **thebigphish** » Mon Jun 14, 2004 9:40 pm

jbxx wrote:Safety officer??
Bwahhahahha.
Quite seriously though, all this will do at the worst
is shut the machine down. No possible harm done.
Quite frankly when you are dealing with somthing that has this much power. You don't rely on any safety devices.
Besides at this point there aren't any.
J.B. AD6WX

i was just thinking? what kind of job-run time will this unit have? if you're pumping out a carrier from a portable while this thing is running...aren't you gonna run into times when you'll suck the batteries dry while the puller is pulling away? From a portable perspective, a job run time that exceeds your available battery capacity will suck..not to mention, portables aren't REALLY designed for extended TX times or constant loads over a LONG time...i mean, a week or so of constatly TXing & changing batteries i think would smoke some finals...heat? decreased TX efficiency? final damage?i don't know, i'm just thinking out loud.

I mean, how often is a portable REALLY pushed past a minute of constant TX? (insert that comment about those moron sgts or lieus who can't shut up) They're not designed for heavy, constant TXing.

kf4sqb · Post by **kf4sqb** » Tue Jun 15, 2004 3:28 am

TX time would definately be an issue. My P1225 hung in transmit for close to an hour one day before I realized it. It still works fine, but it got hot enough that it was rather uncomfortable to hold. If the range isn't an issue, maybe a unit on low power would be acceptable?

BTW, Chris, I love the signiture. Sounds like my wife. Something I am working on will not cooeperate, and I insert the proper expletive, and my wire will invariably ask "what is it"? I tell her to "define it. "It" is a pretty broad subject".

jbxx · Post by **jbxx** » Tue Jun 15, 2004 6:53 pm

Yeh, I don't want to be transmitting full time.
We can be pulling up to a couple of hours.
FRS/ GMRS sometimes will not even talk
from end to end even though we're talking
say 1500' . That 1500' can be in a tunnel.
By the way, these 750 MCM with 35KV insulation
are about 3" diam. each wire.
I think I might have a working solution.
Audio output through a 2n222 to fire an SCR
with a manual reset. Using CTCSS and 5W.
Just needs a little tweaking now.
Thanks for all the input.
J.B. AD6WX

Bob W · Post by **Bob W** » Tue Jun 15, 2004 8:13 pm

jbxx wrote:Yeh, I don't want to be transmitting full time.
We can be pulling up to a couple of hours.
FRS/ GMRS sometimes will not even talk
from end to end even though we're talking
say 1500' . That 1500' can be in a tunnel.
By the way, these 750 MCM with 35KV insulation
are about 3" diam. each wire.
I think I might have a working solution.
Audio output through a 2n222 to fire an SCR
with a manual reset. Using CTCSS and 5W.
Just needs a little tweaking now.
Thanks for all the input.
J.B. AD6WX

If you are talking about firing an SCR with a transistor, then you're not isolated. Not good. Try this... A 120 Vac coil DPDT relay (K1) with contacts sufficient to handle machine current. One side of coil to neutral. Other side of coil goes thru N/O contacts on K1 to N/C contacts on a 12 Vdc relay (K2) on to 120 Vac source. Normally open pushbutton across N/O contacts on K1 (this resets the K1 relay if dropped). Coil on K2 is driven by a CSQ/PL (or DPL) output on something like a Maxtrac. Valid code is received, K2 pulls in, dropping K1. Your load is thru the other N/O contacts on K1. All is isolated, you can explain how it works to anyone, and no falsing from noise.

As far as what you've been doing using a GFI as a big one shot relay.... There's a couple of issues. They are not designed to repetitively break big loads - the contacts burn up, and they fail open. Also, if you are tripping it by causing a current imbalance thru the SCR, you need to know that when you have a large balanced load on it, it's sensitivity is likely to be reduced from the couple of MA that it takes to trip it when there's no load. Also, the wierd current waveform from a motor under load changes the picture. Trip level is still such that it will perform it's intended function - trip if there's enough imbalance to represent damaging current flowing thru a human - UL says that's 5 MA.

jbxx · Post by **jbxx** » Wed Jun 16, 2004 7:16 pm

Thank you for the good reply,
you brought forth a couple of important issues
that I had not considered.
This is a project in flux, so it will be going through
quite a few versions.
J.B. AD6WX