Volume controller circuit - Page 1
Forum section: electronics / beginners

author: prayag2010
author_rank: Contributor
timestamp: January 29, 2012, 05:28:19 pm
content: Hello everyone !!!I am recently working on a project that includes controlling volume using an infra-red remote. I am using an arduino but I am not confident regarding my volume controller circuit. The audio is coming from an ipod and I have attached an image. Looking forward for any reply !!!btw the SUBW_OUT are outputs for a sub-woofer that I am planning to include in this project. The outputs from my circuit are going to an op-amp.

author: Mechatrommer
author_rank: Super Contributor
timestamp: January 29, 2012, 05:58:53 pm
content: 20 npns, 10 resistors. dont you want to consider single IC such as LC7533? (maybe old chip, just came across it in stock, but got no use) YMMV.

author: amspire
author_rank: Super Contributor
timestamp: January 29, 2012, 11:23:10 pm
content: I assume the transistors are meant to switch audio from taps on the resistor chain to an output. I cannot see any way the current circuit will work well. Transistors make very bad audio switches - for one thing, the transistor base switching current gets added to the audio output, so you will get clicks every time you change the audio level. All the transistors with the emitters and collectors shorted become diodes - the last thing you could possibly want in an audio path.The specialized gain control IC's and digital potentiometer IC's are brilliant, but perhaps you want to do your own design.If you want to have your own resistor divider chain, then you will want to use an 8 or 16 channel CMOS analog multiplexer chip. For any of the IC approaches you will either need a dual supply (like +5V and -5V), or you will have to use a capacitor circuit to level shift your audio from ground to +2.5V.If you want something that is simpler that will not need dual supplies or level shifting, it is still possible to get devices called LDR's or light dependant resistors. These as basic two wire devices that go from a high resistance in the dark to low resistance in bright light. So by varying the light from a LED, you could change the volume. LDR's are not really used much in modern designs as the IC's are much better, but it is a good simple device that is very easy to experiment with on the lab bench.If you do an ebay search for LDR, you will find lots of them.Richard

author: Zad
author_rank: Super Contributor
timestamp: January 29, 2012, 11:28:16 pm
content: Use a cheap multiplying DAC. They do pretty much what you are doing in that circuit only more efficiently. You feed the audio into the reference pin and program the level on the DAC digital inputs.

author: beaker353
author_rank: Unknown
timestamp: January 30, 2012, 04:08:29 am
content: What you are looking for is something called a VCA (voltage controlled amplifier). It's in essence an op-amp with an internal feedback circuit and controls the gain by DC voltage applied to a pin. Look inside any true pro level analog audio mixing console and you will find a slew of these bad boys. Typically 2 or three per channel. Analog Devices uses to make a couple chips but I think they discontinued as of now.-EM

author: prayag2010
author_rank: Contributor
timestamp: January 30, 2012, 02:27:56 pm
content: To make my project more simpler, can I use a dual-gang pot ?

author: prayag2010
author_rank: Contributor
timestamp: January 30, 2012, 02:42:37 pm
content: and a servo. I can use an Arduino to control the positions of my servo. So, is it a good idea to do it ?

author: olsenn
author_rank: Frequent Contributor
timestamp: January 30, 2012, 02:59:36 pm
content: Seriously, you should consider a digitally controlled potentiometer like the MCP4131. Connect the source to one tap and GND to the other. If you connect the slider to a non-inverting op-amp you can easily make yourself a headphone amplifier, and with some more digitally controlled resistors you can even add digital control over things like gain and if applicable, bass boost.

author: JohnS_AZ
author_rank: Frequent Contributor
timestamp: January 30, 2012, 03:09:04 pm
content: Have you looked at the TDA7449?http://www.st.com/internet/com/TECHNICAL_RESOURCES/TECHNICAL_LITERATURE/DATASHEET/CD00001657.pdfTwo stereo inputs, volume, balance, treble, bass, and mute ... all controlled over I2C (which your Arduino can handle easily).John

author: JuKu
author_rank: Frequent Contributor
timestamp: January 30, 2012, 03:18:57 pm
content: Also:www.ti.com-> audio -> volume controlLMxxx are ok, PGAxxx for a high-end product.Andhttp://www.cirrus.com/en/products/volume_controls.html, all high-end and even higher.

author: ndictu
author_rank: Regular Contributor
timestamp: January 30, 2012, 04:11:55 pm
content: Quote from: prayag2010 on January 30, 2012, 02:42:37 pmWell at least use a motorized pot, something like this:http://www.sparkfun.com/products/10734BUT, that's just silly. Check the suggestions of digital pot or some amplifiers.Edit: BTW, sound perception (also depends on frequency etc, but that is not so important), so you shouldn't use linear steps.