IR Remote Receiver

[JerryR]

I want to utilize an unused function on my present VCR IR remote to trigger a relay in a stand alone unit(not in the VCR).
To do that, I need to build/buy an IR remote receiver that can decode the command sent ONLY by that function.
Anybody have any ideas on how to do that?
TIA
JerryR

[Chris Smith]

Strip a unit out of an old vcr. start there.

[Edd]

Jerry:
You didn’t get specific on the application of the nearby “unknown device” nor its proximity. Also how frequently that you will be needing to key this device and for what duration….a quick blip or does the unit need to be latched on. Yes, that infrared signal that emanates from the IR transmitter LED of the remote is a function specific multi bit “digital word” of anywhere from 11thru 22 bits…according to manufacturers protocol…….modulating an ~ 38-40 khz carrier. The receivers IR detector/demodulator electronics in the TV,VCR,CD Player, etc takes the received info and decodes/reads it in a dedicated microprocessor circuitry with a branching out to accomplish those specific functions/adjustments/menu access/etc associated with the particular key pressed.
I’ll take an application that I had solved in a different manner, thus circumventing the decoding.
To forego such involvement I concentrated on another characteristic, the time duration of the signal. In my case I was wanting to enact a switching between two antenna inputs. For the sensing of the IR signal , I didn’t even think of using anything but the dedicated small IR receiver module with its IR det diode, optical filtering, and electronics on an onboard chip under an epoxy encapsulant. The unit needs but three connections +5vdc for pwr, the pulse modulated output at about a 2.5v logic level. and the power/signal ground for the unit. These modules are dirt cheap for all that you get, and one could even be salvaged from scrap electronics.
The data output of the IR module goes thru a 1 k isolation resistor and that resistor goes to the + of a 22 ufd capacitor (with a 47K resister also shunting the 22 ufd cap) with caps neg to gnd….. then the same caps+ junction feeds to another 1k which then goes to the base of a 2N2222 relay driver xstr. That xstrs collector goes to a 5V relay and that relays other power term goes to +5Vdc supply.The xstr emmiter goes to ground.There also is a 1N4001 inductive damping diode across the relays coil with anode to collector and cathode to +5Vdc.Also there is a red LED and its series 220 ohm current limiting res shunting the relay to provide a visual of the relays activation. The 5v relay keyed a latching relay in the ant sw box.
The end result was the hold down keying of any remote key puts out a stream of pulses into the 22 ufd cap slowly charging up the unit in about 5 seconds to the turn on threshold of the driver transistor with it turning off shortly after the key was released as the shunt resistor across the 22 ufd bled it down to the threshold where base drive was no longer present. This worked fine for me, as any function that my remote made…. was just a quick blip. The only thing that might deviate from that is some VCR’s that require a hold down for forward or reverse speed search, most units just latch into that function. If the device is triggered by such a condition just reset with another 5 sec activation. The response activation timing may be lengthened by more capacitance where the 22 ufd is or the decay response time can be shortened by lower shunt resistance.<p>73's de Edd
[email protected] .........(Interstellar~~~~Warp~~~Speed)
[email protected]........(Firewalled-Spam*Cookies*Crumbs)

[JerryR]

Edd
Thank you for the quick response, and your possible solution idea.
The stand alone(Unknown) device is a motorized tray that I built into my custom built TV cabinet,
The tray holds the VCR and is normally retracted into the cabinet, a momentary SPST N.O. switch operates the tray(in and out). the relay I want to operate(closure), by remote would parallel the N.O. switch contacts.
Right now I'm using a Salvaged RF remote xmitr/rcvr from a toy car to do this, but that resulted in an additional remote added to the clutter,(hence the desire to use an exsisting remote)
I have few of those IR detector modules(I think that's what chris refers to as "unit" in his post)that you suggested using and I have used them in the past (to extend the range of my IR remote(wired)to other areas of the house).
The remote I'm using does have functions that require that you keep the button pressed(Vol. and Ch. UP/DOWN), but I'll have to experiment using your solution, and see if I can make it work.
Thank you again.
JerryR<p>[ November 07, 2003: Message edited by: JerryR ]</p>

[Edd]

Jerry:
Certainly sounds like a neat/custom feature for your special cabinetry.
If I interpreted the operation right , sounds like you also might want to go ahead and put end of travel microswitches at the drawers extreme in-out limits to reverse and stop drawer action at max in and max out. That way just a quick initial power on of the motor should start it cycling the drawer to either its open or closed position, all on its own.
On my application with the Infrared application, I had done this in days way before such was even available. I know that I was not using any function more than 5 seconds. Typically one just blips TV vol..(as infrequent as it is altered)…and also channel change, or else make direct numerical entry of the channels.
With your further info; 2 more situations come to mind. If the TV happens to be a high end model, it might have an antenna changeover feature in its remote agenda.(None back in my days of course) . That remote function actually breaks out of the remote decoding U/P as an analog DC voltage that feeds an antenna change over relay. One could go to that relays coil and place an optical isolator or small SS relay to get a safe/power isolated interfacing to your separate drawer control electronics.Then just a blip to Ant 2 position would activate output control.This is all being relevant to that Ant Input not being a feature on the TV that you typically would have used.
On a VCR a typical analog voltage breakout of a feature is the TV/VCR function . A voltage goes to the VCR modulators PIN diode RF switching, or easier, the raw 5VDC supply to the VCR’s front LED indicator for that function. Using this particular case, one would want to get that initial 5v level into an optical isolator and then take the OI’s output via a shielded line to a rear 2 term insulated socket /plug. On external control circuitry, that could then interface to a pulse squaring stage and then on to a 2 stage Flip/Flop with an interface to a relay driver ckt on the second F/F. Then a multiple pulsing of the VCR remotes TV/VCR button would toggle the motor start relay on.<p>73's de Edd
[email protected] .........(Interstellar~~~~Warp~~~Speed)
[email protected]........(Firewalled-Spam*Cookies*Crumbs)

[CeaSaR]

JerryR,<p>How about using a current sensing outlet like the one from Sears ( as mentioned in the - I believe - Q & A section of Nuts and Volts sometime within the past few months )? Plug the VCR into the unswitched outlet and then plug a wallwart xfrmr into the switched outlet, maybe run a flipflop or something from that to open/close the drawer. That way, no decoding is necessary, and the drawer will open/close without pushing any more buttons. If anyone has a circuit to do this, please share with us, as I would like to be able to do this at some later date ( have pulsed control of a cicuit when something unrelated is turned on/off ).<p>Hope I helped.
CeaSaR

[JerryR]

Edd.
The limit and polarity(travel)reversal switches are already part of the motorized tray, and a momentary closure of the N.O. switch contact is all that is required to operate the tray(in either direction).
I have considered in the past the idea of taping(hardwire) into the outputs of the remote reciever uProc inside the TV or VCR,(as a matter of fact, I considered using the ANT switch function on the remote xmtr which is not used on this TV) but decided against it, I wanted the system to be independet of the equipment-NO connections between the equipment and the tray system (other than the remote xmtr).
Nontheless I appriciate your thoughts and advice on the subject.
Thank you
JerryR