Volume - remote control? - Page 1
Forum section: electronics / beginners

author: FriedMule
author_rank: Frequent Contributor
timestamp: September 20, 2020, 10:06:02 pm
content: I know I can buy a volume control with a motor but I do not find it necessary to have a motor to turn a pot. So I am thinking if it's possible to make a volume control circuit that both can be adjusted by a pot and by a remote signal?I imagine the physical volume control being some sort of turn thingy I can just turn around, not limited by a min or max, but just read by the internal electronic.

author: ataradov
author_rank: Super Contributor
timestamp: September 20, 2020, 10:46:01 pm
content: Sure, depends on what you are controlling exactly. This is how volume control is done in a lot of cases (any car radio from past 20 years).For the actual input use encoder and for the control either adjust the volume digitally or use digitally controlled potentiometers.

author: David Hess
author_rank: Super Contributor
timestamp: September 21, 2020, 02:50:09 am
content: If I understand you correctly, Tektronix did what you suggest with their microprocessor controlled oscilloscopes 30 years ago. They used potentiometers as encoders so that the microprocessor could override them at any time. Then if the user turned the potentiometer past the point where the control was set, the potentiometer overrode the previous setting.

author: sleemanj
author_rank: Super Contributor
timestamp: September 21, 2020, 02:53:24 am
content: You want a rotary encoder, the rest is just software.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: September 21, 2020, 08:33:30 am
content: Have a look at the PGA2311.The rest is just software, so you can add a regular linear pot with an ADC in your uC, push buttons, rotary encoders, preselect buttons, balance control, cross fading between multiple inputs. All software.

author: FriedMule
author_rank: Frequent Contributor
timestamp: September 23, 2020, 04:50:44 pm
content: Sorry for my impossible late answer!!Yes it can always be made as some software in a microchip but I have to admit that I'd rather work with components then with code-lines. To me is the joy, the building of circuits and making circuit boards. I have programmed many things throughout the time, right from assembler, Turbo Pascal, Delphi, C and lots more.It is just not electronic in the way I hope to learn it.David Hess could you please try to tell me more? It sounds fascinating! :-)

author: ataradov
author_rank: Super Contributor
timestamp: September 23, 2020, 06:30:54 pm
content: In that case you need to be clear what exactly do you want. What does "but just read by the internal electronic" even mean?You need to define what you want to adjust first. The solution will follow from that.But realistically any circuit from discrete components will be digital in its nature. So it will still be an encoder with some counters assembled from 74 series logic. I'm not sure how this is more fun than a trivial program.

author: newbrain
author_rank: Super Contributor
timestamp: September 23, 2020, 07:09:36 pm
content: When I was a kid, my parents had a very nice voice activated remote control.It now goes under the "newbrain" nickname.

author: FriedMule
author_rank: Frequent Contributor
timestamp: September 23, 2020, 09:34:13 pm
content: You are completely correct in that a more precise description on solution would be better but to not exclude any solution, did I ask for every solution, not excluding the programming solution if it was the only sane solution."But just read by the internal electronic" is because of my bad language skills, I'll try to explain.A simple pot has a mechanical wiper that do not change if the amplifier is on or off, it does also not demand any circuit to "know" where it is to work. While a pot-chip that get changed in value, either by some remote control or by turning a button, demands that the turning of the button can be "read by the internal electronic".The "more fun" in building vs a couple lines of code is to me giant. The coding solution is buying an Arduino, write some code and turn it on, not much electronic building in that. Second solution by building with component is to learn about electronic, finding components, making traces and yes building.To me is it a bit like asking what the different between carving a beautiful bird in wood vs getting a 3D printer to make the bird after a few clicks on a mouse. :-)newbrail LOL my parent had also such a device, it was called "Will you please change the channel to xxx" very effective :-)

author: ataradov
author_rank: Super Contributor
timestamp: September 23, 2020, 10:41:42 pm
content: I still don't understand what you want. The resistor is not inherently a volume changing device, it often sets a control voltage to the amplifier. So specific implementation of what you want depends on what you actually need to control.If you really need a digitally controllable resistance, then the only real way is to buy corresponding IC. But they typically have I2C/SPI interface, to may not be trivial to control without an MCU.

author: atmfjstc
author_rank: Regular Contributor
timestamp: September 23, 2020, 11:34:25 pm
content: I think you should first make up your mind about 2 things:1. What should happen, by design, when the physical potentiometer is set to some volume, while the "remote signal" is set to another volume? Which volume setting should actually come into effect? Whichever is greatest? Smallest? Whichever was changed last?2. What do you mean by "remote signal"? Do you mean literally an infrared remote etc., or do you mean any sort of digital or analog signal, even one sent via wire?Unless your "remote signal" is analog, I don't think you'll be able to get away without using anything digital in your project.

author: atmfjstc
author_rank: Regular Contributor
timestamp: September 23, 2020, 11:37:48 pm
content: Also is your "remote signal" continuously transmitting the desired volume, or only when it changes? Does it transmit the actual absolute value desired, or does it transmit only "louder", "softer" etc. commands?

author: FriedMule
author_rank: Frequent Contributor
timestamp: September 24, 2020, 10:03:55 am
content: Love your comments and questions! :-)I do think, thanks to you all, I am better geared to ask.Imagine an RF remote control that sends the signal volume up / down and internal electronic that react on the RF signal by either turn up or down the volume from current value, up some max / min value.On the front of the amplifier is a turn button, connected to a rod that maybe have some magnets or whatever, if the rod is turned, will the internal circuit determine if the rod is turned clockwise or counterclockwise, and do thereby adjust the volume up or down from current value.In short do I think it would be nice with a circuit that adjust the volume and some circuits that read input from the turn button and the RF remote control.

author: ataradov
author_rank: Super Contributor
timestamp: September 24, 2020, 05:58:35 pm
content: So for the mechanical input you need a rotary encoder. The easiest way to read the direction of rotation and the number of steps is though the MCU. Especially given that your RF part is already handled by the MCU.You can come up with some huge circuit that reads the encoder based on the discrete components, but you would still need to get the resulting value into the MCU, since it will have to adjust the volume the same way as it does for RF controlI'm not sure what you are trying to invent here. This mechanism is invented and well understood. There is no need to reinvent it.But if you really want to, then read about rotary encoders, since that the only reasonable way to get infinite rotation. After you see how they work, you can start coming up with a circuit to read it.

author: atmfjstc
author_rank: Regular Contributor
timestamp: September 24, 2020, 07:02:06 pm
content: So it sounds like both the potentiometer and remote signal should cause a plus/minus adjustment to the current value, depending on their relative motion. Software all the way is definitely the sanest solution then. In fact just recently there was a thread about rotary controls that you might find useful:https://www.eevblog.com/forum/beginners/denouncing-rotary-encoder-to-simulate-push-buttons/

author: FriedMule
author_rank: Frequent Contributor
timestamp: September 24, 2020, 08:52:03 pm
content: Again many thanks!! That's why I chose to not exclude any solution, I may not prefer programming but if the alternative is to build a space rocket to do the same, then do programming sound better:-)

author: Doctorandus_P
author_rank: Super Contributor
timestamp: September 25, 2020, 09:08:18 am
content: If you don't like programming, you can use a long stick or a piece of string wound around the knob.Rotary encoders are an often used way to get the position of a rotating axle, but they are not the only option.Another way is to use an endless potentiometer. The magic search words are "conductive plastic" and WDD35.The WDD35 does not have end stops as a normal potentiometer, but it has a small dead zone where the wiper goes from the GND side to the Vcc side. The dead zone is around 10 to 20 degrees (from memory).WDD35 is not a cheap potentiometer, it costs around EUR15, but if you hold one in your hands you will notice where the money has gone:* Strong aluminum casing.* ball bearings on the axle.* Calibrated to 0.5% or even 0.1% linearity.* Rated for millions of rotations.You can also get a kit from Ali / Ebay / China for EUR 20 to EUR30. There are many similar designs. They usually consist of:* PGA2311* Rotary encoder.* HD44780 display.* 8051 class uC.* IR receiver.* Remote control* (Some versions have some relays for switching input channels)https://html.duckduckgo.com/html?q=aliexpress+pga2311+remote+control

author: Psi
author_rank: Super Contributor
timestamp: September 25, 2020, 09:13:39 am
content: Quote from: FriedMule on September 20, 2020, 10:06:02 pmIf you forget about the rotation and just have all up/down buttons you can easily make a system that works.Use a digital pot IC.It has an Up input and a Down input.So you can wire remote IR relay/logic buttons in parallel with the main buttons on the device using pullup resistors and both will work.

author: Mechatrommer
author_rank: Super Contributor
timestamp: September 25, 2020, 10:11:41 am
content: Quote from: FriedMule on September 23, 2020, 04:50:44 pmQuote from: FriedMule on September 24, 2020, 10:03:55 amlets put aside for a moment the controlled part on decoder side... one major part of work is to make encoder and decoder on RF side communicate correctly, and at some level, immune to external noises to avoid havoc control... we usually do it in digital nowadays ie mostly coding will be required. otherwise you'll need to find a fancy (analog) way or circuit in AM or FM radio age for reliable communication. if you dont want coding but still want to go digital RF way, maybe you can search and buy prebuilt encoder decoder IC and put in your RF circuit...https://www.google.com/search?q=remote+control+ic&ie=utf-8&oe=utf-8&client=firefox-bor else, many logic ICs. if you choose analog way, have fun inventing, ymmv.. cheers

author: Zero999
author_rank: Super Contributor
timestamp: September 25, 2020, 12:22:36 pm
content: It depends on what you want to do. I prefer a potentiometer to an encoder, or switches. I find it much more user friendly, so would go for David's suggestion. Use a real potentiometer for user input, read it with the microcontroller, which is used to control a digital potentiometer for the volume control. It could automatically switch between remote and local control, when it senses a signal from the remote, or the potentiometer is moved.As this is for an audio application, you want a logarithmic digital potentiometer, with a linear real potentiometer, as human hearing has a logarithmic resonse, but MCU ADCs are linear.

author: ssashton
author_rank: Frequent Contributor
timestamp: September 25, 2020, 02:30:07 pm
content: Quote from: Psi on September 25, 2020, 09:13:39 amThis is the most sensible soltuion.If you must have a rotating knob, then you need some kind of MC to count the turns and set the volume up or down.You might enjoy playing with one of the ADAU1401 DSP boards. It can be visually programmed in Sigma Studio and has blocks prepared for using a rotary encoder, push buttons or even reading analog voltage from a resistive pot and adjusting the volume accordingly.Quote from: Doctorandus_P on September 21, 2020, 08:33:30 amDon't ignore this.

author: ssashton
author_rank: Frequent Contributor
timestamp: September 25, 2020, 10:36:28 pm
content: I thought I'd post an interesting alternative. I am sitting here listening to music via a Cyrus 'Pre' pre-amplifier. I think it was produced around '95.It is unusual becasue although it has motorised pots, they are inside the case, just sitting there on the PCB not accessible to the user.It has a volume knob on the front, but it is a rotary encoder that is read by a micro-controller. It also has an IR remote control.The micro-controller drives the potentiometer motors seeking a specific resistance setting, so even as the pots wear it is compensated. There are two dual pots because the circuit is differential all the way though. If you manually force one of the pots while it is on, it returns to the previous position.

author: FriedMule
author_rank: Frequent Contributor
timestamp: September 27, 2020, 10:37:33 am
content: You are all fantastic! You do all come with some excellent solutions, but I am not sure what fits my need best, therefore have I used a lot of time to find out of more.I have tried to learn some more and made a drawing to what I think may be the best solution for the attenuation part.To save money, being able to ignore "sound quality" and to be able to ignore noise, have I thought of using two opto-fets as a sort of voltage divider. This can then be done for both channels.Yes I know the opto-fets maybe should be connected in series on a current source, but can't it be done in this way?The idea is that when adjusting the volume control, does one get adjusted logarithmic while the other gets adjusted in reverse log.

author: tooki
author_rank: Super Contributor
timestamp: September 27, 2020, 11:06:18 am
content: One other option to consider, instead of a digital pot, is a dedicated digital volume IC or “sound processor” IC, which will do your digital volume control, but are optimized for it, such that they eliminate any crackling on volume change. Sound processor ICs can also do things like input selection, tone control, etc.In the Bluetooth speaker I designed at work this year, we used a Rohm BD37544FS sound processor chip to handle all the volume, input switching and tone control.

author: Zero999
author_rank: Super Contributor
timestamp: September 27, 2020, 11:37:57 am
content: Quote from: FriedMule on September 27, 2020, 10:37:33 amWhy the opto-isolators? Does it need to be isolated? It can't be to save money. If isolation isn't required, they could be replaced with a single AD5254BRUZ10, or MCP4251.You need to control the current through the emtters. PWMing the voltage won't work very well.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: September 27, 2020, 04:01:34 pm
content: Back in the '70ies volume control was sometimes done with LED's and LDR's

author: FriedMule
author_rank: Frequent Contributor
timestamp: September 27, 2020, 07:54:18 pm
content: My reason for the opto is to galvanic isolate the audio signal from the controlling power, to let the audio run through without having to clean up the power and be able to select the best chip for dimming the opto, not caring if it "sounds good".Also, it could be a "funny" detail to play with, to only have a single FET, acting as the clamp on the signal. But is there anything stopping me in using the potentiometer-chip to dim the opto instead of "dimming" the audio signal? :-)

author: ssashton
author_rank: Frequent Contributor
timestamp: October 13, 2020, 04:33:25 pm
content: If you want galvanic isolation, why not use multi-tapped audio transformers with relays to select the level?Distortion performance of well made transformers can be excellent. Look at Stevens and Billington TX102 as a good example.https://www.diyaudio.com/forums/analog-line-level/258175-stevens-billington-tx102-passive-preamp-built.htmlI had some and tested 2v RMS distortion below -120dB IIRC.LDR (light dependant resistor) are a niece choice for volume contoll. Check out the 'Lightspeed preamp'.https://tortugaaudio.com/top-5-reasons-to-choose-ldr-passive-preamps/