The problem with remote controls is that few constructors are able to understand how they work and even if they could, where could they obtain the parts to build one? OK, you'd buy one of those universal ones and try to program it.

But there is another way, and it's cheap and reliable.

I prototyped one a few years ago, and now I'm going to give it another go and try to make the design available for the DIYer to use in controlling a motorised volume control.

As is normal for me, I will be showing pictures as I go, warts and all, because we like a laugh now and then.

(actually, I'm trying to do something that Bob has been wishing for, for years, but don't build his hopes up)

It is more appealing as you get older.

I forgot about that, good point Jon.

My TVs have all been connected up to the stereo - I've done it for decades.

Initially using RCA phono cables (long ones), and now over Toslink into an external DAC, and into the stereo rig.

Nowadays, with flat screen TVs, it really helps improve the intelligibility and sound, because the built in speakers don't have a cabinet as such to make things better.

My stereo amp has a remote control, so the sound is level adjusted when necessary.

Movies, football, Youtube, iPlayer (and others) all get regularly played over the stereo rig, and all sound much better for it.

What was this bit about optimising your musical pleasure?

What's that all about?

Great speakers are great speakers, and should be able to handle everything thrown at it irrespective of being music or not.

My TV can only go in one place and that's in the corner next to the window, so to get a good stereo image would be a problem plus my speakers need space, as up agaist the wall the bass become's over powering. One speaker in the corner and the other next to a wall is not going to be good for sound quality plus I'd have one speaker closer to me than the other, As it is I have to move them every time I want to listen to my HiFi.

The TV here is in the middle of a flat wall, and the speakers were designed to work well close to a wall.

As anyone got a universal remote control, How do you find it?

How easy is it to program, The one I had was a nightmare, it took me several attempts and like I said, it didn't end well and I sent it back.

agree.

Actually, I was waiting for someone to suggest a jukebox...

And yes, we have rather hijacked your thread, Graham, apologies.

Must be seven years ago when I prototyped the remote control circuit pictured on the stripboards shown in the image.

The problem back then was trying to obtain a trendy looking remote control enclosure, getting everything to fit, how to machine it and how to get somebody to make a pseudo membrane graphic.

Once upon a time I had all the facilities to do all the above, but that was a long time ago, and it ran out of money because nobody in the UK wanted that sort of service.

But it can be made as a hobby electronics project, so I may as well share it with those who'd like to try it. I've read the replies so far, that few so far value the idea, but I still think it worth having a go at.

The only things that I'll have to sub out, is a thin aluminium graphics plate with two square holes, and the firm who does the Voyager panel can do that; and a PCB and that can come from our regular supplier (both in the UK).

The battery will be a 9V E-cell, and the easily obtainable case has a battery drawer.

So, next job will be to draw the circuit diagrams of the remote and receiver circuits, and modify the remote for the larger 9V voltage. You can see it's been a long time by the corrosion built up on the middle 1.5V battery.

The HT12E is intended to drive an RF transmitter, but here it's used to drive an infra-red transmitter. Ideally a HT12A would be used which drives an IR LED via a transistor at the optimal IR remote frequency, except it is no longer made. The reason is perhaps that few used it as an IR remote controller.

The Holtek HT12 ICs are mostly used as garage door openers. But using the HT12E encoder with an IR LED output, it is unlikely it's going to open or close a garage door, and definitely not from inside your home.

Likewise, the HT12D decoder inside the item being remote controlled, isn't going to be affected by an RF garage door opener. And even if a neighbour has an optical garage door opener (if such a thing exists), its range won't be sufficient to turn your volume up or down.

There are also a number of addresses (key codes) that can be chosen, which have to match with the same addresses on the decoder.

Below is the circuit I prototyped around 7 years ago. There are things I've forgotten about how it works, but I shall have a try.

The other IC is the CMOS version of the NE555 timer IC (the 7555) which uses very little current so as to extend remote control battery life.

The 7555 reset is held low until HT12E data out goes high, enabling the 7555 which operates as an astable multivibrator (oscillator) with frequency around 40kHz, and a 50:50 duty cycle.

The HT12E output is at 1.5kHz, so its 1's are "muxed" into around 13 pieces by the IR LEDs. The decoder at the other end will read it as 1.5kHz ish.

The IR LEDs are run at high frequency to enable them to have more current than they're limited to if on at DC.

At 50:50 ratio they can run at 200mA. A single pulse can do 1 amp, but then it's all over, which isn't much use, is it?

On the 6V supply I calculated 130mA, and that gives a radiant intensity of around 100mW per IR LED. It was sufficient to be decoded at a distance of 20 feet with the remote pointing backwards, such that the IR was being reflected by the rear wall. Should be sufficient for any domestic situation.

The power hungry part of the remote is obviously the LEDs and the Darlington configured driver transistors consume a few mA's too. But that's only during operation, and with the 7555 reset pin at logic 0, there's no turn on current to the transistor bases.

That leaves only the quiescent current of the 7555 and the HT12E. The static supply current of the 7555 is typically 50uA and the HT12E is about 2uA.

So, looking at a battery datasheet we see with a 10k load the battery life to 7.5V is 18 days continuous. That's a current of 900uA, and here we have 52uA. All other things being equal, then the battery should last 311 days, or over 10 months.

Is that good enough? It would be nice if it were something like 2 years, but I wonder how.

The HT12E can be powered via the diode matrix, by linking the transmit enable (negative going) to the Vss (-Ve) supply pin. But that only saves 2uA.

We could try powering the 7555 the same way, but there's the possibility it would glitch, sending the wrong code. So the 7555 has to be kept on all the time to be ready.

And that leads me to D1 in the diagram, and right now I haven't a clue why I put it there. That's my memory for you. 

Ah yes, I remember. Vss should not be less than transmit enable, so to ensure it's always 0.6V above 0V, the current for the 7555 runs via it.

Yes, I think you're right.

And that's the reason for D2 as well.

Now, you see all those unconnected pins 1 - 8?

They're address pins, A0 - A7.

For door lock use, they're usually mounted in a key fob using a little key fob PCB and all the pins are taken to VSS. But they use fine PCB traces that can be easily cut, and the same pin traces are cut on the decoder end chip. So there are loads of combinations just like keys.

(in this case 2^8)

This remote control is however limited by the number of functions it can do. There are only four. Here I'm using two - one for volume up, the other for volume down.

The receiver consists of an IR receiver module and was originally a Vishay TSOP4838, which is a 38kHz receiver, and that means the 7555 in the remote should be adjusted to give exactly 38kHz, and not around 40kHz as previously stated (like I said, warts and all...).

The power supply to the remote control receiver circuit is best provided by a 5V regulator, and we'll see that a 1 amp rating will suit it best.

The IR receiver will work from 2.5V to 5.5V and is best decoupled from the rest of the power supply by the typical 100 ohm series resistor and 100nF capacitor (on the datasheet ). Just to be sure, I used a 4.7uF electrolytic capacitor.

The output has to be inverted to be the right polarity for the HT12D decoder, and this is done by using a BC327 transistor with base connected to the TSOP4838 output via a 4k7 resistor. Its emitter to +5V and collector to pin 14 of the HT12D, which is data in (DIN). A 4k7 pull-down resistor from pin 14 to supply 0V acts as the BC327 collector load, ensuring proper switching.

The outputs from the HT12D are the same pin numbers as the encoder's push button pins, so if 10's up and 11's down, then 10 on the HT12D is up, and 11 on the HD12D is down.

The HT12E oscillator is set by one resistor and as it transmits at 1.5kHz, then for the HT12D 5V supply its resistor has to be 75kHz (because it needs to be 50 times and 1.5kHz x 50 is 75kHz) and the corresponding resistor value is 120k, but somehow my prototype uses 100k and works OK.

Except for the HT12D supply pins, the only one left is VT pin 17, which flags a valid transmission by going high (logic 1).

So, we have up on pin 17 and down latches on the output pins matching the button press. The button press outputs latches, but pin 17 only stays high during the button press, so that acts as the stop.

We can then take this as a logic truth table to a quad half H driver chip which is interlocked and when one output is high the other is low, and vice versa, and the pot motor sits between these two outputs!

These driver chips can deliver 1 amp per output, and we can parallel two Half H's together to reach 2 amps. We don't need that much current for the motor as its maximum is 150mA with end stop clutch slipping. But it means the chip runs cooler.

We then only need 4 diodes to soak up the motor back EMF, and that's that.

I'll draw it up next post, but for now I'll comment that I've seen other remote receiver circuits and they're so over complicated it isn't real. Now, they might (or might not) have sufficient logic to bring the motor to a halt instantly, and this receiver circuit simply doesn't and cannot. But how long will it take for the pot motor to stop? It hasn't a flywheel so it must be pretty instant, and I can only guess that it might take 0.1s, and if so it will run past by 2.5 degrees of rotation, which is less than 1%.

We can also experiment by placing a resistor in series with the motor to slow its rotation speed.

Yes, but the pot that's easily available is 100k, unless you're going for an AC30. The choice is yours.

This one interests me  https://mou.sr/3UplN3q - https://mou.sr/3UplN3q

I don't know how you'll house it but keep the wiring short.

UPDATE: see  https://www.holtek.com/documents/10179/116711/HT12A_Ev130.pdf - https://www.holtek.com/documents/10179/116711/HT12A_Ev130.pdf and the DIP version is no longer available. The only encoder is the HT12E (as featured here) but only in 20 pin SOP. Places like Rapid still show availability of the DIP package.

Error on pin 8 L293 corrected (thanks Bruce)

So what will we do in good old Blighty after the economic implosion? Make spears out of flint?

I have on my desk one of these Holtek chips and the packaging says made in Britain! But that was over 10 years ago (yes I know I said it was 7 years ago, but John C set me straight).

These are now made in Taiwan (soon to be a Chinese island?), but we did DIL packages in Britain, so we can do lead-frames, and we lithographed silicon wafers, scored them and microscope operators gold wired them, then we potted them in plastic.

The thing is that employees might not be as particular as they could be, and mask alignment may not have been their forte, so, much silicon was wasted.

And it's the same in Taiwan. They have tons of reject chips just like we did, but their people work for less remuneration, so waste is cheaper.

Now, when engineers die, within seconds all knowledge they had evaporates to nought, and their bodies sleep in the dust of the earth, and decompose. It is likewise with all those operators. The girls (are we even allowed to say girl?) who gazed through stereo microscopes, and with a steady hand, fed the microscopic gold wires, welding between chip land and lead-frame pin - well aren't they entering the realms of the elderly? Perhaps some are also sleeping in the dust?

Isn't globalisation great?

The reason I do these few little projects is to spark interest, to try and enthuse folk to get back into real electronics, and if it worked (which I doubt) then it would lead to demand, and then what?

Ah, but, it was only a dream.

Back in the '70s when I was involved in IC production at Mullards Southampton, memory chips and teletext chip set (remember that?), wire bonding was pretty well semi-automated. These days it's mostly fully automated and once the process is established has high yields.

Where I came across manual wire bonding was in a later career with a specialist company working on thin film microwave stuff destined for radar systems and the like. We were doing mostly customised builds literally by hand under stereo microscopes. The only "girl" we had was an ex-Plessey employee to tidy up our scrappy work and she was red hot at the job!

Thanks for that Geoff. Great to get this information first hand from one who actually did the job!

I can only say what I saw, and I only saw disused manufacturing labs at Ferranti during a chance meeting about something else (the place was demolished a few years ago). All other things have been gleaned through books, press releases and magazine stories, plus the few documentaries on YT.

Through your profile you've allowed us to see your age, and I wish you many more years, but it confirms the gist of what I was saying.

https://www.ditfs.com/control/remote.html - https://www.ditfs.com/control/remote.html

The website is still under construction and so is the remote control project.

Questions about it can still be asked and answered here. However, the threads here don't allow large enough circuit diagrams etc.