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Archive for January, 2015

22
Jan

433Mz Learning Receiver

In my ongoing investigation of 433MHz RF control, I got a new module from eBay today.

433Mhz Module

It runs off a 12V supply and has a SPDT relay. Thus it doesn’t use a MOSFET or something else to control power output, it merely runs a relay to turn things on or off dependant on how you wire it.

And program it…There were no documents with it, which comes as no surprise since it is from off shore and I’m starting to think if you’re born there, you are born with the natural instinct on how all these things work. Or not.

The device is labeled as an “AK-RK01SX-12”. Judging from others I found in this “series” of receivers, the -12 (or -220) is the voltage these things work off of. In this case, it’s a 12Vdc receiver.

The receiver portion of the circuit is not your run of the mill 433MHz one. Rather it’s a superheterodyne version. Thus, better selectivity and sensitivity than some of the other junk I’ve seen.

It is also a “learning” receiver so…according to the eBay listing blurb it can be used to learn those rolling codes you use for garage doors.

The official company description of the module (and yes there is a company website in Chinese that has this info, just takes a bit to find and translate it):

The company design and manufacture of small size 12-volt single remote control switch with 10A relay, can load 1500 watt appliances; can learn multiple remote control, remote control and each can learn all the buttons, a remote control can control multiple switches can also be more than a remote control switch, simple and flexible supporting any combination.

Mainly used in lighting, electric doors, windows, lifting equipment, gateways, lifts, industrial control and security industries.

Second, the technical parameters Operating voltage: DC12V
Operating frequency: 315MHz / 433 MHz

Output: switching signal Maximum load: 1500 watts work: self-locking, jog, interlocking (via pad switch)

Board Size: 41 × 20 × 15mm

Okay. Makes a fair bit of sense. Unless you read electronics.

Notice the 10AMP relay, controlling 1500 watts? If you’re in North America with 110VAC, that would be 12.6A (if you have 110V coming out that’d be 13.6 amps). Want to hazard a guess at how long a 10Amp relay will fair when you’re drawing more through its contacts than it’s rated for? Yeah, me neither.

Secondly, when you get to the line that says, “Output:” and then either the translation fails, or they use a lot different terminology than we do in North America. I’ll cover this a bit further on.

If you look at the photo you’ll see there is a “button” on the module. A single button. And if you’re thinking that must be the “pad” switch, nope. It’s not. Discard that idea. This is the LEARN button.

For programming this is the description I found (translated again):

Third, learning methods

Press and hold the button for three seconds to learn light off, then press any button on the remote control, the indicator light is looked after flash, then learns success.

★ Note: This controller can learn a fixed code (PT2262, SC2260 chip, etc.) / learning code (EV1527, HS2240, etc.) 20 different codes, any button on the remote control, will be followed by purging the oldest beyond learning remote control.

Fourth, the removal method

Press and hold the button down for about 8 seconds to learn the indicator off to recover from a long bright that clear success.

V. Work mode switching

Switching work in different places through the pads 1,2,3 short circuit board behind it.

1. Jog –1,2,3 three vacant land, without connecting

2, interlock – Short 1,2

3, self-locking – shorting 2,3

Notice the “To LEARN LIGHT OFF”? statement? Yeah, I know. So here’s how it works:

Learn:

  1. Press button and hold until LED goes out
  2. Press button on the remote to “learn”
  3. – LED will start to flash
  4. Press button on the remote to “learn” one more time
  5. – LED will come back on, it has learned the code

I noticed that I could use the same procedure multiple times to learn different remotes. So I grabbed my garage door remote. I couldn’t get the receiver to learn the code, it would just time out and return to the LED on mode. On a hunch I checked the frequency of the garage door opener, 318MHZ. Yeah, no way a 433MHz receiver was going to work with that code…

So I have no idea if it will work with a rolling code (although they say it does) or not since I don’t have any rolling code 433MHz transmitters.

Once you have fiddled around with the receiver, you’ll no doubt want to get rid of those codes it learned.

Erase ALL

  1. Press button and hold until LED goes out
  2. Continue to hold button until LED comes back on

It’s back to no codes.

Finally, we have the OUTPUT…according to the translation we have Jog, Self-Locking, inter-locking.

My translation:

  • Jog – MOMENTARY – long as you hold the transmitter button ON, relay is energized.
  • Interlock – LATCHING – Press transmitter, relay energizes. Press transmitter, relay de-energizes.
  • Self-Locking – Press transmitter, relay energizes and STAYS THE WAY. Until you break the connection at pin 2&3.

Flip the receiver over and you’ll find the “lands” or solder pads for the operation of the relay. Thankfully they are numbered.

IMG 0427

  • Momentary – no jumpers.
  • Latching – short pins 1 & 2
  • Self Locking – Short pins 2 & 3

EDIT: The Self Locking feature I originally wrote about was incorrect. One of the commenters was correct in the way it works so many thanks for that Leo!

I got it working correctly with a 4 button transmitter I just received. In self locking mode, I pressed button A to LEARN that code. When I pressed button A, the relay latched. When I pressed button B, C, or D, the relay would unlatch.

When I tried that same setup with a four (and a two) button transmitter I have here, it didn’t work the same way. Relay stayed latched. So…either something wrong with the transmitters I was testing, or the planets were not aligned.

I attribute it to another mystery of the universe.

7
Jan

Arf…Arf…Arf….RF I mean

What’sa matter girl, did Timmy fall into the well? Yeah, that dated me somewhat.

Lately it seems I’ve been playing with more 433MHz transmitters and receivers than normal sane people should have to. It all started with my brother’s truck where we wanted to hide a RF receiver under the hood and control it from a remote to turn on some running board LED’s.

While it worked great in my driveway, after my brother got home to his place, the awesome range we had was pretty much gone. As in 200 ft to less than 1ft. Now admittedly sticking a receiver under the hood of a truck and blasting it with spurious amounts of high voltage in the area and cooking it with the engine heat is probably not good ingredients for the recipe of success.

At the same time, the distance lost didn’t make a fat lot of sense either. The unit I had used is one of the typical ones off fleaBay.

SafariScreenSnapz010

The receiver looks small, but really, inside you could house 6 receivers, easily. And it’s not water proof. Sigh…

Any way I ordered two more of the same units because I assumed that I might have received a defective one. The second one I tried in the house would barely manage a distance of 25 feet and that had to be light of sight. Which makes it pretty much useless.

My next step was to take an Arduino with a 433MHz receiver and see what distance that would get. So I did that. Same lousy distance. Great outdoors though, again, no floors or walls in the way.

This peaked my curiosity as to just how much relative power these little transmitters put out. I built a dead simple field strength tester (two diodes and a multimeter on a millivolt scale). Not to measure absolute power but just to see what, if anything, was happening.

I’ll start with the original culprit, notice the meter is on the 200mv max scale.

Remote Crap

Whopping 2mv. Wow. Doesn’t exactly give you all the confidence that the signal is going to get past the end of my hand.

Next up is a remote LED switch transmitter. These sell for a couple of bucks on fleaBay and I admit the transmitters have given me problems.

Remote LED Switch

Not getting all the warm fuzzies, I grabbed a remote from one of the RF switched powered outlets in the house. This remote will stretch from the work bench at one end of the house to the other. I have an 433Mz transmitter with an Arduino that will simulate it so I know how far it can go.

Power Outlets

Okay, so it’s a bigger number…At this point I am inclined to believe that the receiver on some of these is more finely tuned than I would have expected. Still, that’s not a lot of movement for a transmitter.

Then I remembered a 12V RF relay and matching transmitter I got some time ago. Again, another 433MHz. But this one is different. It has a sliding cover on the case so you can’t accidentally trigger the switch and there is a 4″ antenna with it. I tested it first with the antenna collapsed.

Remote Antenna Closed

This is a MAJOR bump. As in huge…I extended the antenna and retested.

Remote Antenna Open

Okay, jumping from .7 to 9.6 is a fairly large leap. Ah yep.

According to most of the docs I can find these little RF units are roughly 10dbm, or 10mw of power. How far does 10mw go? It’s pretty variable in my experience, heavily influenced by things around it like other transmitters, walls, floors and so on.

I might carry this a step further to see if I can “tune” the receivers to be more accurate than they are. But then again these aren’t crystal controlled transmitters so I’m guessing they splash the signal over a big enough spectrum that you shouldn’t need your clothesline to be able to pick it up. Clothesline. There. I dated myself again.