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Discussion Starter · #1 · (Edited)
Hello

My car has UD71466 CDL receiver module. "Introduction" for 3xxxx series cars mentions, that receivers in those cars work with radio frequency 418MHz. Is it a proper value? Not 433 or 360?

UD71466 is a simple receiver with MC145028 decoding chip. So, it looks like any one-channel remote/fob with MC145026 encoding chip could be programmed to match this module (or any multichannel remote with this chip could be modified to work with). I just want to be sure of proper radio frequency.
 

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Discussion Starter · #2 · (Edited)
OK. Guys, lets say, that there is more sense (and it is more safe) in buying new module with new fob than make new fob for old module. However, if electronics is your hobby, you can try to do it successfully. So...

1. Fob / RC / remote controller / pilot.
There is a main problem, that MC14502x is a more than thirty years old solution. Even if ICs are available at the market, there are no new remotes for that system. You can try to ask about them in alarm or gates companies that worked in '90. It is possible, that needed fob is lying somewhere on the shelf. My fob I bought recently in electronic shop as old DIY set from '00 that way.

2. Programming / coding.
It is the easiest part. MC14502x are programmed mechanically by connecting/soldering three-states address lines of IC to plus, minus or leaved them freely (what means third state). The same way in encoder as in decoder. The code is fixed/constant. You can check your code in your UD71466 module. You even do not need to unscrew it. There is a special flap at the back of the module. There are just 9 soldering points connected to +V, 0V paths (marked at the board) or unconnected. Nine three-states bits give around 19000+ combinations.

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View how it looks inside module.

3. Data rate (internal oscillator frequency fosc).
Unfortunately, MC14502x system does not define standard data rate. Code could be send faster or slower, depended on designer preferences. Fortunately, it is possible to calculate transmitter MC145026 oscillator frequency fosc (and parameters of needed external elements RTC, CTC and RS) based on external elements of MC145028 decoder in UD71466 receiver. Check "Technical data" from Freescale Semiconductor. For my module, frequency is outside of "typical applications" table from MC14502x manual, but predictable. However, as I used in the new fob 4,7nF capacitor instead of calculated 5,1nF (I just did not have it at a shelf 馃ぃ ) and things still work, decoder has quite big tolerance.

4. Radio frequency.
There is another issue. MC14502x can work with many radio circuits and frequencies. Most popular are 360MHz and 433MHz. RR/Bentley, in 3xxxx series cars, used 418MHz. Usually, transmitters have simple, analogue LC circuits with mechanical capacitor trimmer. I believe, that most 433MHz fobs from that era can be just regulated to 418MHz without any further modifications. My new fob was a 360MHz one, so, there was a need to slightly modify LC circuit. You need something like a frequency counter to change/check/measure radio frequency of transmitter.

30119

It's a kind of magic ;)

And that's all folks. If you went through all steps, you can do it 馃ぃ

Anyway, as I wrote at the beginning, it is only a hobby.There is no other sense of this work 馃ぃ It is not worth to do it. If you do not have working fob for your UD71466, just buy modern replacement module with modern fob in the set.
 

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Great info! I'm a sponge for this stuff. Thanks
 

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Thanks for sharing! Wonder if there is a arduino solution? Just to play around..
Btw my keyfob for my car says 433,92Mhz (Toad Security). Maybe they had it changed later!
 

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Discussion Starter · #5 · (Edited)
Thanks for sharing! Wonder if there is a arduino solution? Just to play around..
Btw my keyfob for my car says 433,92Mhz (Toad Security). Maybe they had it changed later!
Sure, it is technically possible to use Arduino, but it is so old solution, that nobody tried that :D It could be easy to rebuild whole system to IR too, what seems to have some sense ;)

Anyway, is there, in your car, UD71466 module mounted at right side of plywood panel in the trunk or a newer one?
 

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Mine is also equipped with an IR remote sensor. But despite changing the batteries, the system doesnt seem to work.
And I have some electrical gremlin to haunt, as my fuse for the CDL always blows.. thus I will check what module I have in due course. Are you also in the facebook groups? Much help there!
 

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Discussion Starter · #7 ·
Oh, looks like somebody already rummage in it...
No. I don't know FB group.
 
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