Tuesday 15 April 2014

AF Amplifier With Digital Volume Control Based On TDA8551

The Philips Semiconductors TDA8551 is a small audio amplifier with an integrated volume control. When operated from +5 V, it delivers a nominal output power of more than one watt into 8 ohms. It can also be used over a supply voltage range of +2.7 to +5.5 V, with correspondingly reduced output power. The output volume can be adjusted from –60 dB to +20 dB in 64 steps, using a set of up and down push-buttons. The shared UP/DOWN input for the up and down switches has three states. If it is ‘floating’, which means that both of the switches are open, the volume remains unchanged. A pulse to earth decreases the volume by 1.25 dB, while a positive pulse increases the volume by 1.25 dB.

AF Amplifier With Digital Up Down Volume Control Based On TDA8551When the power is switched on, the internal counter takes on the –20 dB setting. An additional input (MODE) allows the amplifier to be switched from the operating state to the mute or standby state. If this input is held at the earth level, the amplifier is operational. If +5 V is applied to this pin, the TDA8551 enters the Standby mode, in which the current consumption drops from the typical operational level of 6mA to less than 10µA. Finally, the MODE input can be used as a mute input by applying a voltage of 1 t0 3.6 V to this input. This voltage can be provided by a connection to the SCR pin, which lies at half of the operating voltage and to which a filter capacitor is connected.

TDA8551/TDA8551T Pinout DiagramThe loudspeaker is connected in a floating configuration between the two outputs of the bridge amplifier in the TDA8551. This provides the desired output power level, in spite of the low supply voltage. For headphone applications, which do not need as much output power, you can connect the headphone between earth and one of the outputs, via an electrolytic coupling capacitor. You can make a stereo headphone amplifier in this way, using two TDS8551 ICs. The TDA8551 is housed in a DIP8 package. The SMD version is the TDA8551T, in an SO8 package.

Digital Volume Control

With this circuit you can make the amplifier volume control without having to use a potentiometer, but using a circuit with IC DS1669. For working voltage of the IC of this type was not 5 volts, but 4.5 VOLTS to 8 Volt, but used in this circuit at 5 V because it is more secure than the IC find that you are using exploded.

Digital VOlume Control Circuit Schematic
And the market is a lot of series this circuit of ICs such as:
  • DS1669-10
  • DS1669-50
  • DS1669-100

Number after the hyphen that explains the resistance value of the IC, such as the DS1669-50 means that this ic 50K ohm resistance.
For the datasheet of this IC you can see below.
IC DS1669
Pin Description IC DS1669
  • RH - High Terminal of Potentiometer
  • RW - Wiper Terminal of Potentiometer
  • RL - Low Terminal of Potentiometer
  • -V, +V - Voltage Inputs
  • UC - Up Contact Input
  • D - Digital Input
  • DC - Down Contact Input

Standard resistance values IC DS1669
  • DS1669-10 ~ 10 kΩ
  • DS1669-50 ~ 50 kΩ
  • DS1669-100 ~ 100 kΩ

Tuesday 8 April 2014

How to make home made solar pannel

Solar Panel Build

Make sure to read both the Wind Turbine Build and the Solar Panel Build. Then watch The Tech Junkies Episode #9 that documents it all and puts them to the test!
DIY Solar Panel
Solar has really come down in price since the last time I looked. We wondered if we could start powering our shop off of solar. A good project would be to see if we can build a small scale solar array which would generate power back to the shop and keep it under $1/watt. This would have to include everything from the solar cells to getting usable power out the other end. So we started searching around.

Solar Cell Selection

3x6 Almost Whole Solar Cell Packages
We went to our favorite buying spot (eBay) and did some looking around to see how much we could find some solar cells for. We found that there are production error cells out there that have some blemishes or chipped edges and you can pick these up for dirt cheap….about 25 cents a watt. So we grabbed 2KG worth (they sell them by weight) which will allow us to make about a 500 watt array. The cells are 3.25″x6″ and are VERY FRAGILE! Who knew these things would break if you breathe on them too hard. They are 0.5 VDC with a maximum 3.6 Ampere output meaning they have a max output of 1.8 watts. Since some of them are chipped or blemished we need to figure we will get less than perfect output from them.

Solar Panel Size and Voltage Choice

DIY Solar Panel Construction
We had 9 of the same old windows laying around the shop and they would work really good for about a 50 watt panel each. Wired together they should make a 450 watt array. Really any window panel size will do. Since we are making this on a budget, free windows will definitely help. Making common voltage solar panels helps in wiring them together so they are all working equally. You will lose some voltage from the diode that has to be installed on each panel, but shoot for 12, 18, 24, or 48 volt output panels or arrays.

Electrical Grid Tie Inverter Selection

What exactly is a Grid Tie Inverter and why is that what we want to use? It connects to your existing household AC outlet on on side, and your wind turbine on the other. It converts the DC wind power to an AC pure sine-wave matching the phase of the grid. Since the electricity is being generated on the house side of the power meter, the generated power will actually slow down your power meter or bring it to a stop. But if you are lucky enough to have an old dial turning style power meter AND are generating more power than you are using, it is possible to spin your electrical meter BACKWARDS! I didn’t believe it either until we tried it and it worked.
Grid tie inverters have come down in price and gotten pretty good recently. We expected to pay about 25 cents per watt in this part of the build. They are usually stackable too, which means as your system grows, you can just add another grid tie inverter and they will all just work in tandem.
This is the grid tie inverter we got. It was $138 (27.6 cents per watt) and again we sourced this from eBay.
Grid Tie Inverter

Assembly and Testing

Aligning the Solar Cells on the Window
Here you can see we wired 11 cells in series for each row (5.5VDC). The cells vary voltage from top to bottom and vary current side to side. Meaning if you broke a cell in half 3×3 you would still measure full voltage and have half the amp output. We made 2 full rows, and a third row of cells we broke in half like we just mentioned. Edit: As pointed out by Hack a Day commenter Mark, we effectively limited the current of the entire panel by doing this. This can also lead to overheating in the half panels. At the time, our main concern was getting the voltage high enough for the inverter. For the next set of panels we will be using only full cells. So 3 rows of 5.5VDC = 16.5VDC, then minus the diode voltage drop and we should see around 15-17 Volts Output in operation. We plan on putting 3 panels in series and each series in parallel making a 45-51 Volt (or 48V standard) array.
Solar Cells being Tabbed
It makes it easier if you pre-wire a lot of cells before you start. Here you can see we started making piles of them. It really goes quick and is pretty easy to get the hang of once you do a few. The trick is to get a soldering iron that can get hot enough to make it so you don’t have to spend a lot of time on any part of the panel for too long. It took us a few hours to build a 50 watt panel. That time involved will play a part in how big of a system you want to start with.
DIY Solar Panel Wired
The cells get wired together easily by running “tabbing” wire down them after applying a flux pen. This make soldering to the solar cells painfully easy. Here you can see all 33 cells wired in series. With each full 3×6 cell theoretically capable of producing 1.8 watts and the halves at 0.9 watts this would be a maximum of 49.5 watts. We’ll round and call this a 50 watt panel.
DIY Solar Panel Taped
Once all the cells are wired in place, we tape everything down and give it one last electrical test. This will temporarily hold it in place while we pour a two part polyester resin epoxy over it all to lock it in place.
DIY Solar Panel Epoxy Back
Here is the epoxy sitting to harden up. When we made this we used old epoxy in cool temps and it came back to bite us. Ours peeled up and ended up taking so long to set up that it leaked through our masking tape and got under some of our panels. We figure we now need fresh epoxy and use about 1/10th of a gallon or less for this size panel. A little goes a long way and really this is just to give it a thin seal and lock everything in place.
DIY Solar Panel

Results and Thoughts

Here is the breakdown of our costs:
$125 Solar 3×6 cells creating 500 watts worth
$0 Windows
$50 Gallon of Epoxy
$25~$50 Tabbing wire and diodes
$138 Grid Tie Inverter
————-
So for roughly $375 we have built a Solar Array capable of producing 35-50 watts in it’s current state, with a maximum of 450 watts if we can get full sun. If we did this again we could get the price down even lower, but for about 75 cents per watt it would only take a few years for us to pay this system off.
The next step on this project is to finish the rest of the panels and tie them all in together and see some long term power generation to get an average for a year. Our first panel puts out about 35 watts in full sun, so we have some improvements to do for the next one.

Let the government pay for 30% of your alternative energy generation project!

As we were digging around with this project I want to make you aware that there are some really good government grants (AS IN FREE MONEY!!!) for those that take advantage of them. As always consult with a professional before deciding to spend any money and never take my word for it. But for what it is worth this website has a lot of good information about getting financial assistance in building alternative energy sources. Check out http://www.dsireusa.org/ to find out if your state has any local policies. As of the writing of this, as long as you START your build before the end of 2011 the Feds will pay for 30% of your project if it is under a commercial business. There are LOTS of grants and loan programs out there to help pay for the costs of installing these systems and now seems like a great time to do it. Earth will love you for it too.