IR type remote control devices

[kinarfi]

If I'm not mistaken, remotes work off a series of pulses at a specific frequency and maybe PWM and that varies from model to model and make to make. Also, the receiver is darkened to filter ambient light, BUT, if a brighter visible LED is used at the correct frequency, will the receiver still receive the signal?
I have an Alpine CHM-S601 CD changer and the remote doesn't seem to want to work any more, I can get it function occasionally, but not consistently and Alpine is supposed to be sending me the specs on the output and I hope to be able to build a device using 555 timers to operate the CD changer. If any one has a RUE-4175 remote they want to get rid of, that would be sweet.
Also, on several devices that I have disassembled/torn apart, I found the receiver to be a dark 3 pinned device and I think it is a receiver/transmitter, do modern remotes receive as well as transmit? Does anyone know what a BU3406F chip is?
Headed for google to see what I find.
Thanks

 

[Nigel Goodwin]

If I'm not mistaken, remotes work off a series of pulses at a specific frequency and maybe PWM and that varies from model to model and make to make.

'Sort of' - it's a series of digital pulses of an ultrasonic carrier - various schemes are used, 'changes' of pulse width is one, and Manchester coding is a VERY common one. Whatever is used it's important that accurate pulse widths aren't used, as the pulse widths don't transfer anything like accurately.

Also, the receiver is darkened to filter ambient light, BUT, if a brighter visible LED is used at the correct frequency, will the receiver still receive the signal?

It depends - visible light could well swamp the receiver.

I have an Alpine CHM-S601 CD changer and the remote doesn't seem to want to work any more, I can get it function occasionally, but not consistently and Alpine is supposed to be sending me the specs on the output and I hope to be able to build a device using 555 timers to operate the CD changer.

Use a PIC or similar - you 'could' probably do it with a large heap of 555's and logic chips, but it's not something I'd like to attempt - and who wants a remote control that's larger than a laptop?

If any one has a RUE-4175 remote they want to get rid of, that would be sweet.
Also, on several devices that I have disassembled/torn apart, I found the receiver to be a dark 3 pinned device and I think it is a receiver/transmitter, do modern remotes receive as well as transmit? Does anyone know what a BU3406F chip is?
Headed for google to see what I find.

The 3 pin IC is a receiver only, and a complete IR receiver and demodulator - it outputs a representation of the original digital pulses.

The BU3406F is obviously the remote control transmitter chip.

 

[KeepItSimpleStupid]

There are all sorts of encoding. One of the main ones is Pulse Position Encoding. In a lot of cases now, there is usually a pre-amble that allows the receiver to develop some sort of AGC. (auto gain control).

Some older IR receivers don;t get along with Plasma TV's, CFL's or high outdoor light.

Modulation is typically 38 or 30 Khz, but I have an early unit that uses 70 kHz.

There can be addressing modes to allow more than one similar CD player to respond to different remotes.

Learning remotes don;t always work especially because of the implementation of repeat.

Two start bits are better because of the AGC issue.

Some IR controls send the bits and then the inversion for a more robust transmission.

So, basically, the 38 Khz carrier is turned on and off for a set time for on and a set time for off.
Usually delays set the inter-bit time and the inter word time. It is a complex process.

The receiver, usually requires +5, gnd and an output and will have the "recovered" pulses with the carrier removed. The receiver incorporates an AGC and an IR filter. as well.

Another thing that's loosely important is that the 38 Khz may not have a 50% duty cycle. The lower the duty cycle, the less power required by the remote transmitter.

 

[dr pepper]

Infra red remotes use manchester coded data with address/data and toggle bits, or pulse position modulation just to name a couple, this would as Nige says be tricky and complicated with discrete logic.
There are intelligent remotes that learn, but thats no use without the original.
One for all do a range of remotes that have a built in modem and can be flashed by holding them to the 'phone, if a file is available for alpine this might sort you out.

 

[kinarfi]

Thanks guy, I did some research on google and I agree that it's too much for 555s, would it be very difficult to do with microcontroller?

 

[dr pepper]

If you can find out the standard used, alpine might tell you if you get the right person, theres probably a few projects on the net knocking about that'll do the job for you.

 

[Nigel Goodwin]

Thanks guy, I did some research on google and I agree that it's too much for 555s, would it be very difficult to do with microcontroller?

It's absolutely trivial with a PIC, there are examples for Sony SIRC's in my tutorials, but I've used the same basic transmitter code for many different remotes - it's simply a question of knowing the exact data stream you need to create.

 

[kinarfi]

Turns out the remote control is OK, where the problem is, is in the semiconductive dots on the switch domes the make the contact when you push the bump down. While I was testing it, I make a scope shot of each function and then made on .png from all of them, definitely not something I could do with a mountain of 555s. Is the any way to make the dots more more conductive? I thinking I'll cut some dots of aluminum from some aluminum duct tape and stick over the black dots.

 

[rumpfy]

Over time, the dots and the base contact material gets covered in crud from greasy fingers and the odd drop of cocacola.
Take the thing apart and clean the PCB by washing with methylated spirit. Use a cotton swab and get the crud off the pcb.
With the silicon rubber bit, clean this down with metho on a cotton bud. Clean each dot.
Check the resistance across the face of the dot. This should be less that about 10 to 20 K ohm. If higher, then a bit of repair might be needed. Just check first though. To repair the dots, I use some graphite lubricant. There is a material use for lubricating piano actions and it is graphite mixed with a solution of ethanol and other stuff.
Its important with these remote controls not to flog them too hard when they become hard to use; pressing hard seems to transfer more of the carbon material to the PCB.
I've cleaned many of these things, and some earlier ones were hard to get working so you may have to persevere with applying the conductive repair gunk. Ultimately you will succeed. I've thought to try an aluminium piece as you say, but the graphite is the way to go.

 

[kinarfi]

Thanks for the advice Rumpfy, I took the push pad from my fluke and it worked well on the remote and the resistance of the dots was in the 2 Meg ohms region and that was with EZ hook probes, not pointy probes, so I guess I need to go find some graphite.
Thanks
Kinarfi