Interfacing different remote control systems...

[wedderwedder]

Its me again....
Firstly - i have managed to take some pictures - will upload them later on. You can see the tracks a bit more clearly on these so.. Wait and see the clarity.
Anyway - Steve - I tested the Resistance and got 1M ohms on most until the button was pressed then that dropped to very little when pressed. I then tried you 'Careful' poking about with the -ve terminal and the pins... Nothing happend when i touched the -ve with ANY pin. I was super careful and have tested the remote since (it still works thankfully) We even set up a spectrum analyser with Antenna Input to check whether the RF was firing but not the LED (our usual indicator of the remote working) this showed that NOWT was happening unless i Pressed a button.. then all is fine.. Grrrrrrr. Its annoying being rubbish at somehting that would be so simple to you guys. One thing that may help you is - The LED flickers when 'on' it is not a constant 'on' i am wondering if, in conjustcion with the IC there is an oscilation tha the swtich itself is connecting rather than just an 'off - on' would this be a reason for more terminals on the switch?
Anyway i will leave you to muse - tut about teaching numptys on the web - wonder why you started this with me, and generally take deep breaths. The photos i upload later will hopefully help a bit. As for the optocoupler circuit, i will not attempt to rebuild that until i know where to stick it.. so to speak. Thanks again

 

[(*steve*)]

I would imagine the remote sends a coded signal repeatedly when the button is depressed. The LED may simply be flickering in time with this.

If you can read the part number of the IC I may be able to locate some specs. It's possible that may shed light on this.

 

[wedderwedder]

Right - Its really hard to read the writing on that chip.. but this is what it says (i am 99% sure)

EMC
EM78P156ELMJ-G
0701A BTSO6CD3

***That Red 8 might be a 2**

ANy help???

 

[Mitchekj]

http://www.datasheetcatalog.org/datasheets/700/238920_DS.pdf

That looks like it may be it? Definitely not my forte.

 

[wedderwedder]

couple more pics for you guys, alot better than the last lot anyway,

thanks again for your time on this.

 

[wedderwedder]

How about..
1. I tape down (somehow) the buttons
2. I break the track from battery to the switch(s)
3. I use the opto coupler thing to re-make the track and hence turn on the switch

this is not an ideal answer for me but will it work? Obviously the best solution would be a way without the tape..... But by the sounds of it chip is a whole new level of complication.

Hope you suddenly think of the answer )

 

[Mitchekj]

I would think Resq's original idea would work something like this:

The opto would apply ground to the pins, just like the switch would when you manually press it. You could solder the optos straight onto the remote's PCB, on the switch's pins.
This is assuming, of course, that the switch is applying a ground to the pins they connect to, which from what I can tell would be the case. All depends on how they have that chip programmed.

Then, I got to thinking that maybe they're using the 6 leaded switch as a way to cut down on the connection resistance in the switches. 3 contacts in parallel would cut down the resistance. I don't know how sensitive the chip is when it comes to low-hi, etc.

If that were the case, you may have to find a really low RDSon FET (low-low milliohms) and figure a way to drive those w/ the optos. Larger gauge wire would be in order, as well.

Anyhow, see attached, this is how I envisioned Resq's idea. Hope this helps a little.

 

[(*steve*)]

Well spotted Mitchekj.

Wedderwedder, the pictures are *much* better. It looks like the circuit uses a microcontroller to control the oscillator. The photos are now good enough to identify the 433MHz resonator and to see the various components that make up the RF section.

However the shadows around the switches make that critical part of the board difficult to make out. The areas I'm really interested in are the connections to the switches. I want to try to deduce where the tracks go *under* the switches.

Taping down the switches *might* work, but then you'd need 2 remotes, one for up, and the other for down (I guess). Also the optocouplers may not be able to switch the power reliably without a little more assistance.

You could test the concept by removing the battery, pressing the switch, and then momentarily inserting the battery again.

Mitchekj, that is right, but omits an additional resistor that is required between the 12V and ground to give the capacitor a discharge path when the 12V is disconnected.

The switch would not be passing any significant current. It is highly unlikely that the switch contact resistance is an issue. What is far more likely is that the switch is applying power to the circuit *and* also a signal on another pin (to determine the function). That would explain why poking around and making only one connection at a time had no effect. If this is true, the switch is probably DPDT, and this explains the 6 connections neatly too.

If that assumption (DPDT switch) is true, then wedderwedder's idea of taping down the switch and switching the battery would almost certainly work.

 

[wedderwedder]

Kinda update and questions.......
Firstly i took off a switch and - well that was confusing.... It has a part that links two pins, then when you press the switch down it connects a different pair of pins whilst also having an arm that moves sideways to connect something else..... I just should not have looked. This is some weird stuff electronics! Does this help anyone at all?

Secondly - i am working on my great idea of breaking the track form each switch to the battery then use the opto coupler to re-make that contact - Anyway i do not think the unit is 'ON' for long enough. It just flashes a TEST led for less than half a second.. is it easily possible to extend the 'ON' time to about 1 full second? DO i just need to purchase a larger value cap>???? if so er.. help......

Together we will solve this (oh ps - i have not got the unit to flash an LED when i switch off the power yet.. i thought i would get to this last.. lets get it to do the first switch for now)

 

[Resqueline]

There shouldn't be any need to break tracks, only to add couplers in parallell to the switches. Just measure what pins are (independently) connected and we can imitate that.
The IC is what you suspected, and it's not originally intended for remotes, hence the need to switch power to it too.
(ps - did you add that extra resistor to the switching voltage as mentioned 2x earlier?)