Simplest, minimalistic remote control (1 button, on-off) - Page 1
Forum section: electronics / projects

author: Sredni
author_rank: Frequent Contributor
timestamp: April 04, 2023, 12:43:48 am
content: I am looking for ideas for building a minimalistic (on-off toggle) remote control for a single 5V appliance to be placed in the same room (where a TV and its own remote control are located). No other such devices will be present in the same room.I know there are commercial remotes that can be bought for 5 bucks, but I am looking for a DIY solution that is both minimalistic and simple (meaning: possibly without custom ICs).The best solution I've found so far is to use a microcontroller (like an ATtiny85) and an IR receiver, paired with an existing remote control and a relay module (or a soft toggle switch). Like thishttp://www.technoblogy.com/show?V6F,or this:But it uses an MCU and requires programming (nothing bad with this, but I would prefer an analog solution).My second thought was to use an unused button on the TV remote (does not matter which because this system will be stupid), that needs to be pressed for at least a couple of seconds so that the receiver can charge a capacitor to a threshold voltage that will make a flip-flop toggle, and using the flip-flop output to command the relay or the soft-switch.This of course is a 'stupid' system in that it might toggle with the volume button (a button that can be pressed for more than a second) but it's more or less an acceptable behavior (that can be mitigated by placing the IR receiver in a position that would require to point the remote at it).What is your 'simplest' solution?

author: james_s
author_rank: Super Contributor
timestamp: April 04, 2023, 03:26:08 am
content: Are you wanting the challenge of building something or do you just want to have a working remote? If the latter you can buy remote controlled outlets, I used to had one that had a single button keyfob type remote. Ikea also has their Tradfri line of zigbee based smart sockets that can be paired directly with the remotes they offer.

author: Sredni
author_rank: Frequent Contributor
timestamp: April 04, 2023, 05:17:01 am
content: I am looking for a DIY solution that could come out of a McGyver episode. A post-apocalyptic survivalist hacker circuit made out of recycled toothpicks and paperclips. Well, maybe not used toothpicks, yuck. But the most basic the components, the better. I am also willing to build the flip flop out of transistors to avoid adding a 4017, for example.I am aware of the commercial solutions available, and they would cost much less then building what I want. But the circuit I am looking for has to be the opposite of general (I mean, the ATTiny85 solution is brilliant and can be scaled to several devices): razor sharp focused on the one job it has to do, i.e. turning on and off a single 5V line (coming from an USB charger - I could also do without a relay).I am also oriented toward an optical solution because being able to use the TV remote will avoid me to have another gadget that will most likely end up lost somewhere when I need it.It's one of those circuits I want to build 'just because', not because I have a real need or the alternative would be too costly. Quite the contrary.I was looking for brighter ideas than these two I havehadfound so far. (The one I had is the second one, the MCU one I would have built with an Arduino, but that's too much stuff)

author: james_s
author_rank: Super Contributor
timestamp: April 04, 2023, 05:53:14 am
content: You could try modulating the IR light at a specific frequency and then use a bandpass filter to trigger on that frequency. The earliest TV remotes I remember seeing were ultrasonic and used a similar approach where the frequency of the sound would trigger various actions. Early multichannel radio controls for model airplanes used vibrating reeds to decode the various commands, I suspect the TV remotes used a similar arrangement but I've never seen the schematic of one.

author: tooki
author_rank: Super Contributor
timestamp: April 06, 2023, 11:46:44 am
content: Quote from: Sredni on April 04, 2023, 05:17:01 amI like the idea of using an unused key on an existing remote. But doing this categorically rules out an analog solution, as you must decode the remote control commands.IR remotes work by pulsing the bits of the IR protocol with a carrier-modulated IR emitter. The most common carrier frequency is 38KHz (NEC standard, by far the most common), but 36KHz (Philips RC5, Panasonic) and 40KHz (Sony SIRC) are also common, and others are in use. So for NEC, it means a 38KHz square wave is turned on and off to send the bits.To receive them, you use an IR receiver module designed for your carrier frequency, and ideally one specifically optimized for the protocol in use. The module strips off the carrier frequency and outputs simple high and low pulses.You could then use a small MCU running an existing IR receiver library to decode the IR commands. When it matches the key code for your desired key, then you switch.Note that remote controls send each command a few times for redundancy, and that depending on the key and the remote, held-down keys may repeat the same command over and over, or they may send adifferent“repeat” command so the receiver itself can choose to handle a held-down key differently from repeated discrete presses. (In your case, you’d ignore the repeat command.)I think you see why there’s no way you can do this with an analog circuit.

author: jpanhalt
author_rank: Super Contributor
timestamp: April 06, 2023, 12:34:33 pm
content: Apparently the LM567 tone decoder is still available. Don't know whether they are available in Antarctica. A tone based system (e.g., 555 to generate tone, LM567 to decode) would be simple. In the 1950's we used tuned relays (aka reed relays, as the LM567 wasn't available).EDIT: By "tone" I meant sound, light (IR), or RF modulation.

author: james_s
author_rank: Super Contributor
timestamp: April 06, 2023, 05:11:39 pm
content: I forgot about the LM567, I think my Heathkit GC-1000 clock uses one of those to detect the tone at the top of the minute on the WWV broadcast.

author: Kim Christensen
author_rank: Super Contributor
timestamp: April 06, 2023, 07:04:57 pm
content: And then there is the old "clap switch". No remote required.Might be a problem if you watch a lot of loud action movies with gunfire and explosions.

author: jpanhalt
author_rank: Super Contributor
timestamp: April 06, 2023, 07:31:23 pm
content: I was thinking along that same line with sound. Premade receivers are available, so someone with a violin, piano, horn, or good voice could make it work too.

author: james_s
author_rank: Super Contributor
timestamp: April 06, 2023, 08:42:53 pm
content: It ought to be possible to decode IR remote transmissions without a microcontroller, but probably not with an analog circuit. They're generally only a byte or two, shouldn't be too hard to clock them into a register and decode.

author: Sredni
author_rank: Frequent Contributor
timestamp: April 06, 2023, 08:59:25 pm
content: Yes, the 'stupid' solution I had come up with is to use an IR receiver (or just an IR photodiode), filter its output and then use a diode and capacitor to extract a signal when the sensor is hit by the pulsing IR coming from any remote button. The longer I press the button, the higher the voltage across the capacitor, and that can be used to trigger a relay or a soft switch on the 5V line.The clapper solution suggested above is another possibility. I wonder if I can make it sensitive only to certain sequences of sounds, like hitting a glass or a cup with a spoon a few times (with the right temporal sequence)... A sequence like...I need to experiment a bit with those capsules to see if I can tell apart hand-made sound pulses.I could even attach a piezo sensor to the fridge and tap a sequence on the door :-) - but let's keep the command 'remote'.Of course, as far as component count go, nothing can beat the ATtiny MCU + IR receiver IC combo.

author: jpanhalt
author_rank: Super Contributor
timestamp: April 06, 2023, 09:27:44 pm
content: Quote from: Sredni on April 06, 2023, 08:59:25 pmThe range of your photodiode will be very limited. You need a purpose made IR receiver module.QuoteParallax makes a nice sound detector based on the MAX9814 chip. The break-out board includes a microphone.Anything that needs to read a serial signal (e.g, a series of claps -- more than, say, 2 or 3) will most likely need an MCU, which was one of your design criteria not to have.I thought you wanted to be DIY and avoid an MCU? Did you change your mind?

author: Sredni
author_rank: Frequent Contributor
timestamp: April 06, 2023, 09:38:11 pm
content: No, what I was thinking is to convert the above sequence into a digital sequence, and then consider it as a clocked digital signal and use a sequential circuit (old school) to identify its occurrence. I just need the "Shave and a haircut" part, not the last "two bits".

author: Psi
author_rank: Super Contributor
timestamp: April 06, 2023, 09:48:50 pm
content: Anything really really simple wont have any checking to confirm what was received was actually the signal you expected.And the thing may turn on/off randomly from random signals.That's why no one does remote control that simple.

author: Sredni
author_rank: Frequent Contributor
timestamp: April 06, 2023, 10:01:47 pm
content: Yes, that is true in general if you want a highly reliable remote with many buttons. But I only need one button and I can tolerate a false triggering here and there.Music is fundamentally a clocked signal with a strict 'tempo'. So if I can reliably turn a sequence of knocks with reasonably timed pauses into a digital pulse train with a clock of say half a second, I can hope to be able to decode an improbable sequence without false triggering. Maybe I will have to repeat it to get my tempo right, but what are the chances the blender will make a "shave and a haircut" series of sounds?(The actual sequence could differ, and I can see the difficulty in getting it right when the amplitude can change with distance from the receiver - this is just an idea in progress)

author: james_s
author_rank: Super Contributor
timestamp: April 07, 2023, 12:06:39 am
content: If you want to go with IR and an existing remote I would suggest first starting out with a purpose made receiver module, these will give you a ready to use digital signal and with that you can work out how to decode it. Then if you want to do it all from scratch, build an analog circuit to demodulate the 38kHz or whatever bursts and convert them into the digital pulse stream. Or go the other way around and build the demodulator first, but you're going to need a demodulator either way. You want a nice clean digital pulse stream similar to what you'd get out of a UART on a microcontroller.

author: Psi
author_rank: Super Contributor
timestamp: April 07, 2023, 01:36:49 am
content: If you simply feed an IR photodiode/transistor signal into an 38khz bandpass filter, then slow down the output with an RC filter and use that to turn on a transistor and relay when ~38khz IR is present for more than a few 10's of ms.Then you will have a basic remote control that should work from any button on any IR remote.It's a horrible way to do it but it fits your super basic 'MacGyver' requirement.The filter could be opamp based or just passives.That's about a simple as it gets.