Category: Electronics

Simple USB powered Audio Mic Mixer

Here’s a simple Mic mixer that can be Powered with 5V. There is currently 3 channels on the circuit but you can add more if needed.

About the Circuit

The circuit is made up with BJT common emitter configuration. OPAMPS that can operate at low voltage are hard to find at a local electronic stores. The very common TL072 opamps can still operate at 5V at a very limited output voltage swing.

The circuit provides ~29dB gain, you can reduce that gain by increasing the value of the emitter resistors(R8,R9, and R11).

R3 and C1 is a filter for the power supply. C1 can be increased to reduce the noise if your power supply is noisy. R3 can also be increase up to around 100 ohms for better filtering.

You can connect this circuit to the USB audio interface circuit in this post so you can have this connected to you PC for recording.

Simulation

On the simulation below I used waveform generator with sinewave output at 100mV at frequencies 100Hz, 200Hz and 500Hz respectively. The volume setting is set at 30%, 10% and 10% respectively.

Build this Simple but amazing USB Audio interface for only $5

In case you want to connect your audio mixer or electronic piano or any other line level audio equipments to your computer or laptop for recording, here is a simple USB audio interface circuit that does the job. It is based of PCM29XX IC from TI. This is used in many analog audio mixers with usb interface such as the Behringer Xenyx USB mixer series.

About USB audio interface circuit

This circuit is USB powered. The IC has 16bit delta sigma ADC and DAC and capable of up to 48kHz sampling rate. it has stereo line level input and outputs.The crystal needed is 12MHz.

 

Quick PCB design

Here is a simple PCB layout that I designed using kicad software.

3D Render

simple usb audio interface PCB design
simple usb audio interface PCB design

Want to have a copy of the Kicad design? Just like my facebook page and send me a message. thanks for visiting… 🙂

Prototype

Since I needed this circuit for my recording may piano and guitar covers, I built my own using universal PCB. This is what I used on my guitar and piano covers on my youtube channel here. 

At first time try, I am having problem with it. Windows shows an error message “Device not recognized” when I plug this to my Laptop’s USB port. Upon hours of troubleshooting, I found out that C13 and C14 is causing this issue. These are the capacitors connected to crystal oscillator. When I tried to removed these capacitors, the issue now gone. I tried to lower the value from 22pf to 15pf but it didn’t solve the issue. I also tried 5pf but same thing happens. For this prototype I just removed C13 and C14. Maybe because there is parasitic capacitance on the board that I used.

There’s no need for drivers, it installs automatically when you plug it in. It has 16bit ADC/DAC with up to 48kHz sampling which is good enough for recording. 16bit/48kHz might not sound great but it is actually good. This chip is used by Behringer on some of their Xenyx USB mixer and also on their cheap usb audio interface. The audio quality is not the best but it is better than those cheap USB sound card on the market. This is good enough for recording for you youtube content. 

Video

Here is the actual video of my prototype in action.

Please subscribe to our YouTube Channel. 🙂

USB audio interface Parts list

RefValuePart
C11u16V electrolytic capacitor
C20.1uceramic capacitor
C34.7u16V electrolytic capacitor
C44.7u16V electrolytic capacitor
C51u16V electrolytic capacitor
C61u16V electrolytic capacitor
C71u16V electrolytic capacitor
C81u16V electrolytic capacitor
C91u16V electrolytic capacitor
C101u16V electrolytic capacitor
C114.7u16V electrolytic capacitor
C124.7u16V electrolytic capacitor
C1322pceramic capacitor
C1422pceramic capacitor
D1LED:LED
J1USB_B:USB connector
J2Input3pin JST connector
J3output3pin JST connector
R12.2 ohmsResistor SMD or 1/4W or 1/8W
R21MResistor SMD or 1/4W or 1/8W
R31MResistor SMD or 1/4W or 1/8W
R41.5kResistor SMD or 1/4W or 1/8W
R522 ohmsResistor SMD or 1/4W or 1/8W
R622 ohmsResistor SMD or 1/4W or 1/8W
R71MResistor SMD or 1/4W or 1/8W
R81MResistor SMD or 1/4W or 1/8W
R91MResistor SMD or 1/4W or 1/8W
R10220 ohmsResistor SMD or 1/4W or 1/8W
U1PCM2902CUSB interface IC
X1CRYSTAL12MHz Crystal

The parts list does not include input and output connectors, you may opt to use RCA or phone jack connector.

I am planning to build an improve version of this device and sell it online so stay tuned! Subscribe to my youtube channel and facebook page to keep you updated! 🙂

DIY DI Box v3

I just noticed that many of my visitors are searching for DIY DI Box so I decided to make another design project for DI Box. This will be powered by a 9-15V AC/DC adapter or a 9V battery.

About the Circuit

The circuit is basically made up of 2 opamps, 1 is configured as a buffer and the other one is configured as an inverting opamp.

R2 and R3 is used as a voltage divider to provide 1/2VCC for the opamp. This is needed for single supply operation of opamp. At single supply, the output of the opamp cannot swing at negative voltage so the output of the opamp is offset to 1/2VCC so the output can swing below 1/2VCC for negative voltage and above 1/2VCC for positive voltage swing. at the output stage, a capacitor is used to remove the DC offset and output only the AC voltage. C5 is used to filter the 1/2VCC from the voltage divider R2 and R3. R1 and C1 is used to filter the supply. This is used to filter out the 60Hz/120Hz line noise on the supply. If you are using a battery, you can just remove R1 instead. Potentiometer value can be 100k to 1M. I used RCA connector simply because I can’t find any Audio phone jack on my library and I don’t have time to search for it.haha

C6 and C7 voltage rating should be at least 50V, this is to protect the cap when phantom power is accidentally turned on. Other capacitors can be rated 16V and above.

Phantom Powered DI Box

If you want it to be powered via Phantom power of mixer, you can check this version of my DI Box here: https://tataylino.com/diy-di-box/
You just need a 1/2W 6.8k resistor and a 15-30V zener.

PCB Design

PCB design is made with KiCad, a free open source software. Designed with 1 layer PCB for easy DIY at home.

3D Render

100W Amplifier Project

Here’s a simple 100W amplifier project  that is based on Elliot Sound Products project posted on his website.

Simulation Circuit

For the simulation I used TIP32C and TIP33C for the power transistor because there is no available TIP36C and TIP 35C on simetrix. They are almost the same but the TIP36C and TIP35C is capable of handling more current thus capable of delivering more power.

Simulation Result

Schematic

PCB Design

PCB design is done using kicad software. It is a free software. The PCB is only 1 layer so it will be easy for most DIYers out there.

NOTES:

  • The size of the 2200uf and 100uf capacitors on the layout are only assumed. Those capacitors comes with different sizes, depending on the manufacturers. Check the actual size first before making the board.
  • Capacitor voltages are 50V.

3D Render

3D render of the board with kicad built in 3D render.

POWER SUPPLY

You can use 25Vx2 10A transformer for the supply. The diode can be any rectifier diode rated at least 100V and 12A.

DOWNLOADS

you can download the project on my download page below:



Download Page

Simple 2 way crossover project

Here’s a active 2 way simple crossover project for you.

About the circuit

The Circuit is simple and uses only 3 opamps per channel.

Crossover frequency is set around 234Hz. The cutoff(crossover) frequency can be changed for your requirement. The formula for the crossover frequency indicated below:

C4 is used to block DC voltage at the input. Since the input impedance of the circuit is very low, C4 value can be as low as 0.022uF. But for my final circuit I have used 0.1uF.

R3 and R4 are voltage divider used to provide half VDD voltage for the op amps. This is required because the power supply has no negative voltage. Without this, the output will be clip on negative cycle. C3 is just a filter capacitor to clean the voltage produced by the R3 and R4 divider. R5 is used to set the input of the input buffer to half VDD, 1Meg value is used so it will have little effect on the input impedance.

Simulation

Simulation result

As expected, the crossover frequency is around 234Hz.

PCB

For PCB design, I made it single layer so most of the DIYers can easily make their own PCB. As usual I used KiCad to design the PCB which is a free software. Resistors on the VDD are just jumpers(that is why it has value = 0).

J1 – Right input

J2 – Left input

J4 – Low Right output

J5 – Low Left output

J6 – High Right output

J7 – High Left output

J3 – Power Supply (12V – 24V)

3D Render

3D render using KiCad…

DOWNLOADS:

This project can be downloaded for you own personal use. If you want to use this for commercial use, please contact me on my Facebook page for licensing. 🙂

Please don’t forget to like my facebook page. 🙂

Download page

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Hybrid Solar Power for LED TV and Electric fan

Philippine electricity is the most expensive in south east asia and it is getting more and more expensive every month. With the solar panel getting more and more affordable, is it really worth it to invest into solar power system? How much can you save with your electricity bill with these solar power system? How much will it cost to build your own? Let’s find out!

Types of Solar power

There are basically 2 kinds of solar power system and they are 1. On-grid 2. Off-grid.

On-grid Solar Power system – basically a solar power that is tied to your existing AC power from meralco of whatever your electricity provider is. This is the simplest system since it is only tied to your existing electrical power system. It is sharing power to meralco if the power is not enough to power your house. For example if your devices or home appliance is consuming around 1000W of power in total and your solar power can only produce 600W of power, the other 400W will be supplied by Meralco. This will in turn lower your bill because you will only consume 400W instead of 1000W because your solar power will handle the rest. While if on the other scenario, if your solar power system is generating power more than you need, it will be feed the excess power to the grid and will be bought by Meralco. In this case you will be a power producer to the Meralco instead of a consumer. Meralco will pay you for the power you generated. Take note that the rate at which Meralco will pay for your generated power will be way lower than what you pay for meralco per KWhr you use. Take note also that you will need to apply for net metering so you can be able to selll your excess power to Meralco and the process is not easy. There are many documents and procedures to follow before you can qualify for net metering. If you have no net metering, you might be charged when you are producing more power than you need. This is because normal meters are not designed by bi-directional current flow. So be careful with this kind of solar power system.


image from: http://energyinformative.org

The main disadvantage of On-grid solar power system is that when there is brownout, you also experience it. This is because Electric systems on each house are connected in parallel and you solar power system will overload if it will try so power during brownouts.

Off-grid Solar Power System – by its name suggest, this is not connected to your existing electrical power system. And because it is independent by its nature, it needs a battery for powering at night when there is no sun. And batteries as all we know are not cheap! And most of all, you need to replace it very 2-3 years(depending on type of battery and usage). This makes this system more expensive as compared to On-grid systems. The main advantage of this is that you can build this system anywhere as long as there is sunshine. And the biggest advantage is that you will never experience brownout as long as your battery is in good shape.

Hybrid Solar Power – This kind of solar power is just my idea, I don’t know if someone already thought of it. But because this system is very simple, it is most likely that someone out there might already built this kind of system. Block diagram below:

 

 

I call it hybrid because the output is 12V instead of 220V compared to on-grid system and it uses your existing AC power when there is no sun to power your system. I made this system so I won’t be needing expensive battery compared to off-grid systems and won’t be supplying power to the grid compared to on-grid systems.

About the Circuit

The circuit is simple, you have 2 power sources that set at slightly different voltage. The solar panel is connected to a buck converter which reduces the voltage of the solar cell from 19V to 14V. An AC/DC switching power supply is set at around 12.7V to compensate for the diode voltage drop. The output voltage of the solar is set slightly higher so when there is enough solar power, it will pull the output voltage to around 13.3V(-0.7V diode drop), this will reverse bias the diode D2 and will act like an open circuit. If the power from the solar is not enough, both diode will conduct and the output voltage will be just around the voltage output of the AC/DC converter.

Boost converter is used to increase the voltage to 19.5V to power my 32 inch Sony LED TV. I am not sure if most of the LED TV uses 19.5V but if I remember it correctly, my LG LED TV also has 19.5V supply.

What You need

On this project, those materials can be bought from online shopping like lazada or shopee.

12V output AC/DC converter

To make it more reliable, use a type with output current double than what you require. This will reduce heat and will have longer life.

BUCK Converter with adjustable output voltage

Set the output voltage to 14V before installing this. Make sure also that it have higher output current capability than what you require.

Arduino programmer is not responding problem

Just recently I made a project with arduino nano and used my old working board. To my surprise I got an error that the programmer is not responding. After some debugging I found out that there is no problem on my wires or drivers. It looks like arduino just updated their bootloader with no backward compatibility. There is not option on the board “ATmega328P ( Old Bootloader)” but it doesn’t work.

So I decided to just re-program my arduino nano with the latest bootloader. The bootloader hex file can be found on the directory below:

To program, I used power debugger and connected it like below:

After I programmed the latest bootloader, my arduino is alive again. 🙂

The real problem here is that arduino updated their bootloader with no backward compatibility. The best fix is to program your arduino board with the latest firmware that you can find on the arduino folder on your program files directory. You can use any AVR programmer. You can also use your working arduino to program another arduino here: https://www.arduino.cc/en/Tutorial/ArduinoISP

 

Super Bass Tone Control

If you love to pump up the bass then this would be great project for your sound system. This is based on my previous tone control design with some modification to give more deeper and louder bass. It is basically the same with modified component values.

ABOUT THE CIRCUIT

The signal amplifier circuit is composed of R1-R4, C1, C2, C7, and Q1. It is configured as common emitter amplifier. It amplifies the signal because it will be attenuated on the next stage. R4 and C1 is used as low pass filter to filter out the low to high frequency ripple voltage of the power supply. It basically cleans the power supplied to the circuit. C2 and C7 is used to remove DC offset from the transistor bias. They are DC blocking capacitors, it passes AC and blocks DC. R2 is used to bias the base of the transistor to set the voltage of the collector to somewhere around the middle.  R1 and R3 sets the gain of the amplifier. To increase the gain, decrease R1 or increase R3. Always check the bias levels after changing the value of R1 and/or R3 as this might result to signal distortion.

CIRCUIT SIMULATION

Simetrix is used in this simulation. A free simulation software for individuals.

Bass Response

The problem with this kind of circuit is that the frequency response is not linear. The graph below is sweep from 10% to 100% bass setting with 10% interval while the treble is set to 50%. As you can see, the response is almost flat around 10% bass setting instead of 50%. It has around 12dB of bass boost at 50% bass setting.

Treble Response

Below is the frequency response of the treble control with the bass set to 50%. There is 12dB bass boost at 50% bass setting. The treble setting start at 10% all the way to 100% at 10% increment.

Adding output buffer

The problem with this circuit is that it changes frequency response with the next stage input impedance. If the amplifier has a volume control, it affect the frequency response.




200W Amplifier Design

Here’s a 200W amplifier design for your home audio. It is a class AB amplifier. It is capable of delivering more than 200W at 4 ohms.

About the Circuit

There’s nothing special about the circuit, you can find it all over the internet nowadays.

Simulation

I simulated the circuit using simetrix software. You can download the simulation circuit on our download page so you can play with the circuit and component values. Be mindful on the power of the output transistors.  You can increase output power by adding output transistors but you also need increase the supply voltage. You need to take note that the output transistor TIP3055 and TIP2955 can only have VCE max at 60V. In practice you don’t want to get near to that voltage. The safe supply voltage for this transistor should be around 45V.

PCB Design

The PCB design is simple and used 1 layer PCB only so anyone can build this project easily. You can also download the project on our download page if you want to modify it for your own requirements. My PCB design is simple and there are many rooms for improvements. The size of the filter 1000uf capacitor may be small in actual, you may need to check this before making the board. If you can change it with 2200uf capacitor then that would be better. But take note that this will be bigger capacitor. These capacitor are used to help supply power during big current draw. These high current draw usually happens during bass drum beats, especially if you set your bass to maximum. Supply voltage drops during bass drum beats due to high current draw and power supply output impedance.

These capacitors also helps reduce hum noise by filtering ripple voltage coming from the power supply.

The high current nodes such as power supply and output can be improved by making the trace wider. By making the trace wider on those nodes reduces voltage drops on those trace. This can improve bass performance.

3D Render

3D rendering is build-in on the KiCad software and this software is free!

Power Supply

This circuit can be powered by 24V up to 32V transformer. The transformer should be center tap and at least 8A for single channel.

 

image credits: interfacebus.com

NOTES:

If you want a very reliable design that doesn’t easily fail for years, the key is over designing. Design it to handle 200W and operate it at 100W and expect it to have longer life. This is because there is less stress and heat on each component if it is operating below its power handling. If you have computed that a resistor will consume 0.2W then use a 0.5W resistor or larger. Using a 0.25W resistor will still work but will eventually burn overtime.

DOWNLOADS





You can download the Kicad and simetrix project on our download page

3band tone control using transistor

Here’s a simple 3 band tone control circuit with 1 transistor instead of using opamps. This is using a single 12V supply. The frequency response is not as good as with using an opamp but it is still acceptable provided you just want a way to boost bass, treble, and mid frequencies. The transistor used is a BC549 but this can be replaced by any general purpose NPN transistor like 2N2222, etc.

 

VR1 =Treble
VR2 = Mid
VR3= Bass

Simulation result

As expected the response is not as good as what you can get with using an op-amp version but it is good enough for home sound system where you don’t need a very flat response. Each of the controls can affect the whole sound spectrum.

Bass Response at 0%, 25%, 50%, 75% and 100% setting

MID Response at 0%, 25%, 50%, 75% and 100% setting

TREBLE Response at 0%, 25%, 50%, 75% and 100% setting

Extreme settings:
green – bass = 100%, mid = 50%, treble = 100%
red -100%, mid = 0%, treble = 100%

As for the graph above, the mid setting will greatly affect the treble response. This is still good to use is you just want to boost bass frequency.

MIC Preamp type Circuit

The circuit above can be used for mic preamp. This is a simple but not outstanding. The performance is just ok for low end home audio. But for high performance audio, you should go with opamps especially made for audio applications.