Ever since becoming active in Part 15 I have been adding frequencies to the game. Right now I lay claim to 3 AM frequencies, 3 FMs, 1 long wave and 1 shortwave. Not all of those frequencies are developed yet, namely the carrier current and long wave, but they will be soon. There may also be a 900 mHz STL (studio transmitter link). Of course, all of the transmitters are spread far apart from each other to avoid mutual interference. Turning them all on or off takes about 5 or 10 minutes running between them. That’s why I am now designing a remote control system so they can all be controlled from one location.
Getting a focus on how to proceed with the remote controlling circuitry has been a study project for a long time, but the other day I found a circuit in a book which I absolutely love and this will be the starting point. Keep watching this blog because I am going to scan the schematic and invite comments plus I have some questions.
I have the fondest memories of the clunky rack mounted remote control rig that controlled the 70 kW FM where I worked. It contained a literal telephone dial on it’s front panel and by dialing “2” and “raising” the filaments the transmitter, 10-miles away, would warm up. A meter displayed the filament voltage so I could verify it was turned on. 10-minutes later by dialing “3” I would “raise” the carrier, and the needles on the frequency monitor all stood up and the speaker monitor went silent with a city-wide carrier.
The smaller version I am building will show by LED which transmitters are on. I won’t need to lease a phone line because all the wiring will be a private little home-owned “phone system.”
I will be opening a project page at kdxradio.com for the remote control system, and the information will belong to the Part 15 community.
RFB says
PIC Processor
You could go further and program a PIC microprocessor so you can control several units with only one set of controls. The PIC could also be programmed to display your TX power, current, tuning peak etc etc.
Just a thought! ๐
RFB
Carl Blare says
Idea Accepted
Thank you RFB. I am adding your suggestion to the project. I know that using a microprocessor to do the job would be very rewarding.
When I had a Commodore 64 I had engineering help and was able to use the parallel port to turn 8-relays off/on using “poke” commands on the computer. This was programmed in with the onboard computer clock and I was able to cause tape recorders to stop and start at pre-programmed times. Actually I still have two Commodore 64s in storage, but I think what you are proposing will be smaller and smarter.
I will start with the circuit I mentioned, and then go through the evolutionary processes of “upgrading” to better systems. It will be a technologists dream like running a model railroad with a growing passenger base.
rock95seven says
Now wheres that darn remote
A station i worked for had remote control over a phone line. Well basically you would call the transmitter, a voice would give you options and you would press the buttons on the phone to adjust power, stand-by, get swr/power readings and if i am not mistaken some basic diagnostics.
Very cool.
radio8z says
Wireless Remote Control
Carl,
Consider getting a “multibutton” remote control system similar to those used in cars. The ones I have provide two to four control outputs so they could perform multiple functions with one unit. They run on 12 volts and will drive relay outputs and some provide latching functions such as on/off.
Web search on “wireless remote control” and you will see many sources for these.
Neil
Carl Blare says
My Starter Circuit
My starter circuit, which I intend to build first before moving on to other types, uses a TRIAC instead of a relay. Even though the particular TRIAC shown in the circuit from a book is now obsolete, I will have Mouser help me find a modern version.
Soon I will post a picture of the diagram.
The type remote you are describing, Neil, can be built on top of my “on/off” version.
RFB says
RFC-1
“you would call the transmitter, a voice would give you options and you would press the buttons on the phone to adjust power, stand-by, get swr/power readings”
Sounds like the Sine Systems RFC-1 unit. I have two of these units, one of which is currently tied in with my main on air transmitter (TX-30) which has been geared for remote control and sensing.
Ring…..ring…..ring….
“Enter Code”
“Hello…this is XXXX”
“Channel 01…XX”
“Channel 02…XXXX”
“Enter Security Code…”
“Ok”
“Goodbye”
For a remote control system that talks back…at least it could have been programmed to hold a decent conversation, or curse you out for leaving it all alone out there in the middle of nowhere! Maybe something like…
“Hey you idiot….turn down the power!”
“Hey you lazy goofball, get your butt out here and sweep the floor and get this dead field rat off of the transmitter diode stack!”
RFB
Carl Blare says
Not The Same Thing
A field rat is not the same thing as a field inspector.
RFB says
Smarts
“A field rat is not the same thing as a field inspector.”
Any field inspector dumb enough to go sticking their hands into a 10KV diode stack of a running transmitter deserves every bit of jolt they get!
A field rat at least has no idea. ๐
RFB
Carl Blare says
Rodents and Shocks
One day I tried to catch a mouse by putting a flat bowl of water down on the kitchen floor, with a sheet of metal on the bottom of the water attached to 110VAC, a small coffee lid had a piece of cheese. I forget the exact design, but from two rooms away I saw the mouse get shocked over and over and over but it kept coming back to get that cheese. Either it never associated the shock with the cheese, or it felt it was worth it.
I did not patent the contraption.
RFB says
The Zipper Zapper Mouse Trapper
I would have made a 20Khz switching circuit feeding a junk tv high voltage transformer and used that instead of plain outlet voltage.
Rest assured, that rat would be zapped and stiff as a brick on the first jolt.
Go a step further and make a remote control for the zipper zapper mouse trapper complete with arc sensing and scent sensing. Maybe even tie in a webby cam for that special visual effect and post a video on youtube! That should bring in the votes!
Just make sure you put up a disclaimer stating that you are getting rid of pesky rodents and not purposely trapping and zapping innocent rats! Keep the animal rights folk happy.
RFB
Carl Blare says
TRIAC Remote Control
The first circuit to be used to turn transmitters on is shown here
http://www.kdxradio.com/lph_files/remote_triac.JPG
I need to find an equivalent for the obsolete TRIAC, then need to find whether this or similar circuit will control lower voltage, such as 24VAC or 12VAC.
Later, other remotes methods will be tried.
RFB says
Interesting
An interesting control concept. However using an active element such as a TRIAC only adds more complexity to the concept of simple…not to mention adding something that could flake out and cause more than your transmitter to turn off….that is if the fuse does not react fast enough.
If it were me, I would use the trusty reliable SPDT relay and configure it so that a simple momentary contact switch provides the power to the relay, and the second contacts maintain that relay in the “on” state. Then simply add a normally open, momentary un-contact switch to remove the supply from the relay for the “off” state.
Just tossing ideas.
RFB
Carl Blare says
Re-Trial
Request for a re-trial of the TRIAC circuit. Here’s what the author says:
With switch open, transformer blocks gate current, prevents the triac from firing and applying power to the load. Closing the switch short-circuits the secondary, causing the transformer to saturate and trigger the triac.
Does this change your mind about whether this will work?
Carl Blare says
About Relays
The reason I have been avoiding relays in designing a remote control system is because of the constant current they draw while latched. I am looking for a circuit that only pulls current during activation.
radio8z says
Triac Control
Carl,
The triac circuit you linked is not a good design. It is very likely that the triac will fail due to high current inrush into the gate. Also there is no provision to attenuate switching hash will will probably put a buzz in your signal.
I have used 12 volt automotive general purpose relays such as this one: http://www.google.com/products/catalog?q=12+volt+automotive+relay&hl=en&gbv=1&prmd=imvns&um=1&ie=UTF-8&tbm=shop&cid=5551894296188177115&output=nojs . They don’t draw much current (about 100 mA) and can be powered from either your transmitter supply or a surplus DC wall wart.
Another option since you are running a line anyway is to just place the switch in series with the DC supply to your transmitter. Since you will be switching low voltage/low current DC there is no special requirement for the wire. 18 ga. speaker wire would suffice.
Neil
RFB says
TRIAC 101
“Does this change your mind about whether this will work?”
No not really. It will work, but not without problems…a lot of problems. Well maybe not a lot but some problems that will no doubt cause other problems…potentially hazardous I might add.
“The reason I have been avoiding relays in designing a remote control system is because of the constant current they draw while latched.
Well this would be true if you were to use big bulky sledge hammer relays. I agree with Neil, there are small DIP relay packages that barely pull milliamps and some even less in packages the size of 8 pin IC’s. These run on DC voltage potential and have very good isolation between their contacts.
Your only concern with using relays is making sure its contact ratings will handle the current load of the transmitter power being fed through it. Too little contact ability to handle the current, even in the milliamp world will cause pitting and arching on the contacts, in turn causing noise spikes and the all too familiar “POP” in audio stuff, and even go across your audio in the TX and across the airwaves, not to mention that irritating intermittent contact relay that although latched on, it isn’t passing voltage or current to the load unless it is tapped or moved around.
This is more prone to happen if your switching 120VAC through the relay coil via one side of the contacts, or any large voltage, large current device on the load side of the contacts. But there are very simple remedies to solve that. .1MFD 3Kv ceramic caps across the contacts will absorb the contact spikes as well as prevent pitting on them. MOV’s can also absorb these spikes.
But your TX’s are all low voltage DC units that are not drawing amperes of current. Just take each unit’s total operational voltage and current draw and get a DIP relay capable of a higher contact rating.
So if your TX draws 300 uA, find a DIP relay with contact ratings at say 500 uA, or a 1A rating if a 500 uA cannot be located.
The DIP relay packages won’t overload the stock wal wart supplies most use on these low power transmitters. As I said, they pull very very little current, some as low as tiny grain of rice bulb.
A much better approach to switching 120VAC circuit paths is to use solid state relays meant to handle 120VAC directly. A bit more expensive than their old “click and bang” counterparts but far more reliable and equipped with internal noise cancelling. Depending upon the current draw of the load, some may require being mounted to a heat sink and heat sink compound used for maximum thermal transfer.
If you desire to go the “non mechanical” way, you can use a simple NPN transistor as a switch to apply power to the transmitter. With a small bias voltage (turn on) to its base, the current will the flow from collector to emitter (ground) and turn on the device. Run the TX’s power ground to the collector of the transistor. The emitter to power supply ground. Use a 3 volt regulator powered again by the power supply powering the TX and run the regulator’s output through a resistor divider network to bring down the 3 volts to a more friendly bias voltage for the transistor, just enough for it to turn on and conduct but not saturate its base junction. To find the right transistor for the job, simply examine the transistor’s maximum ratings and use one that is above your operational voltage and current ratings. Also take into account the .7 volt drop across the collector/emitter junction. At the low DC voltage supply of 12 volts, the .7 drop wont really affect anything but you should be aware of it for overall design parameters. A simple one-shot “flip-flop” circuit can serve for the proper “on” and “off” states for the base bias control of the switch transistor. This arrangement means you only need 1 momentary contact push button type switch to control both the turn on and turn off function.
RFB
Carl Blare says
Unemployed Triac
Thank you gentlemen for guiding me about TRIACS. I have given the idea the heave and will look at other solutions.
The circuit is in a big fat book called “The Encyclopedia of Electronic Circuits,” and I have found many of the circuits in the book to be skimpy, lacking adequate detail. The author must have pulled a fast one on the publisher.
Doing it all low voltage is my true wish anyway.
Back for more discussion when I come back from the think tank.
RFB says
Electronic Reference Circuits
“The circuit is in a big fat book called “The Encyclopedia of Electronic Circuits,” and I have found many of the circuits in the book to be skimpy, lacking adequate detail. The author must have pulled a fast one on the publisher.”
I doubt the author was intending to fool the publisher or anyone else.
Much of the circuits found in books such as the one you mentioned are good circuits and meant as a starting point, a base reference to build from. As Neil pointed out, your circuit has no hash cancellation or real protection, which the author provided you with that starting point circuit. Its up to you to determine what can be added to increase the circuit’s functionality and/or safety factors.
The concept you came up with is not a bad idea, but it is bare bones and you would be working with dangerous voltages and currents that do require careful consideration during the design stages.
RFB
Carl Blare says
Need To Do
When the CC transmitter goes full time I’ll have a problem. It’s not remote controlled at its location deep in the cellar.
Over a year ago I started this thread, but never did the work.
Some excellent suggestions were made in this thread, and now I’ll open the page on my website for this project.
Almost started.
Carl Blare says
No Progress Yet
I want to keep track of this thread because it contains some good tips on remote control over a part 15 transmitter.
This project is slow because of me, a slow guy.
But this project is the real deal and will move forward when I open a dedicated web page on the subject.
As I see it I will build several side-by-side methods for remote control, a kind of living laboratory of alternate methods.
Today I am thinking about the DC power supply that will provide power to the remote panel.
Are there any remote control methods in use that haven’t been reported here?
Carl Blare says
Progress is Remote
Wow, I opened this thread way back in 2011 and only this morning started thinking about continuing.
Progress to date: zero.
Let’s RESET.
o.k, so I’m planning to build a tower way out back, about 100-feet behind the Internet Building (the tool shed where I sleep by a transmitter).
A. We’ll need to get power out to the 3-meter tower. Can we have a single voltage that will serve all needs, like a 24-VDC system? Maybe the power can be “phantomed” on the balanced audio line. It will probably need to be wired, since there’s not enough sun view to stick up a solar panel;
B. The balanced audio line is basic, but it is conductive and might be yet another path for lightning. Why not a fiber link?
C. The remote control. That’s the main subject of this thread, but it will be tied in with all the other stuff so I see it as all one compound problem.
Wonder if I ever opened a project page on the subject?
Carl Blare says
Remotely Uncontrolled
None of this remote control project has been done.
My brain is hung up on getting the wires from the cellar out to the tower (100-feet).
Problem one – Where to punch a hole in the wall;
Problem two – Shall wire be buried or above ground.
Decision expected by sundown today.
Carl Blare says
Remote Thoughts
Sending electrical power over wire is more efficient using alternating current.
Yet the only way to send phantom power over an audio line is to use DC voltage.
The reason for combining audio and power on a single line is to employ one long line instead of two.
This is another decision faced by the designer of a remote controlled transmitter installation.
Comment period is open.