redwire

Did you look up 555 monostable mode?

I have used Processing to build a nice GUI for the PC in order to send commands to an XBee connected to the computer, which send the command wirelessly to another Xbee connected to a microcontroller (Atmel). The site is www.processing.org. I know Arduino and Studio have hypertext window that will communicate but you are limited to text and data with no pretty background, pictures, buttons, gauges, graphics like Processing can provide.

Understand. I'm about to purchase a Rigol DS1074Z so I can have a 4 channel view. I think it may take a couple of weeks to arrive.

Liquibyte, Although I quoted our discussion it was really a general statement for the board. The project is advertised as 0-30V and many individual have discussed disappointment when they can not get to zero volts. After reading over 140 pages of discussion, you designed your board to utilize a expensive film cap in pursuit of achieving true zero volts. Based on the results of your build and tests, it appears that the film cap really doesn't provide any substantial improvement over the electrolytic cap. Your boards are already made so I am certainly not suggesting any change to your boards. Your tests are helpful and further the discussion on this board. For those who come after, and expect to achieve the advertised project with easy to get parts, simply changing a connection may be the solution. It would be simple to test by cutting the trace to pin 4 and putting a jumper wire to the negative rail. RV1 may need to be adjusted .

While the current design works well and all parts work within safe operating conditions, I think the current design needs to be changed to connect pin 4 of U2 to the negative rail (-1.3V), rather than ground to be able to adjust the voltage to a solid 0. U2 would still be operating within it's design parameters.

liquidbyte, what is the lowest voltage setting you are able to achieve with no load?

Does adding another shunt resistor to this PS, outside of the feedback of U2 and input of U3 have any negative effects on the voltage regulation. I don't know the value of the shunt resistor but what about current regulation.

Have you considered something like this: http://www.adafruit.com/products/296. Using AVR Studio 6 (free)you only need a usb cable to program the chip. No separate programmer is necessary. If you plan to do future project then you may want to consider a Dragon. I have a STK500 it is a bit bulky but rugged and versatile. The breakout board I linked is small, fast, powerful and has enough pins to handle most projects.

It is not the programing language that will be the controlling factor but the microcontroller and set up. Many AVR chips (used on many Arduino's) have 10-bit resolution (2 raised to the power 10) resulting in 1024 different reading. If you use the chip's internal reference voltage of 2.56V you will get 0.0025mv resolution. Now this means you need to have a voltage divider from your PS output to the microcontroller that limits the sensing voltage to 2.5 V. Some AVR chips do allow you to use a 1.1V reference getting you close to your 1mv range but things may get jittery when trying to measure at that level. I bet you will find your display jumping in increments greater than 1mv. I think you will find 2mv accuracy is good enough. You will likely need to do some tweaking in software (averaging, offsetting, sampling rate, etc) to negate sampling error and tolerance in transistors used in the voltage divider. You will probably want to add a trimmer to your voltage divider set up, so that you can fine tune without needing to reprogram. If you don't have a lot of programming experience, I think Arduino is the way to go. You can build your own pcb shield that fits on top of the Arduino. This is a breakout board that I used C to program from AVR Studio 6. http://www.electronics-lab.com/forum/index.php?topic=19066.msg1015257#msg1015257 . I believe you can include the Arduino Library and program using Arduino as well as straight C in AVR Studio 6. My goal was to make the board so I can use on other projects so it has a lot of extra stuff. I got sidetracked and never finished because of a fundamental power issue of trying to feed 41V from the power supply thru a bunch of zeners to get 5V to power the chip. It works but the Zeners get burning hot. I'm going to drop back and use a small transformer and bypass the zeners.

The two things to adjust are: 1. Voltage limit. The 20K trimmer connected to U2 is to limit output to 30V. You will likely find that the 20K trimmer straight from the factory was set at approximately 10K and is right about where you need it. Set P1 to the maximum output, then adjust the the 20K on board trimmer to get 30V on the output. 2. Current limit. Without a load on the PS, adjust P2 so that you have the maximum voltage on pin 3 of U3. Now adjust the 100K trimmer on the board to to limit the max current that the board will output. Because you are using a 0.47 Ohm Resistor , Using V=IR, If you want a 3A limit, the maximum voltage on pin 3 of U3 would be 3A x 0.47 Ohms = 1.41 V. So adjust the 100K trimmer so that the maximum voltage on pin 3 of U3 is 1.41 volts. You can fine tune from there. Neither of the above adjustment will bring the voltage to exactly zero. You will probably find that if you have small load on your PS you can bring the Voltage down 0. If you still want zero with no load, touch a 5k or 10k resistor across the output points on your header blocks and see if that brings the voltage to zero. If that does the trick you can permantently connect it to your output header block along with your output wires.

One way would be to acquire a Arduino board. Then program one input (horn button) and 4 outputs signals to a relay board such as http://www.amazon.com/SunFounder-Channel-Shield-Module-Arduino/dp/B00E0NSORY/ref=sr_1_6?ie=UTF8&qid=1397060045&sr=8-6&keywords=relay+for+arduino which power the speakes. Write a pretty simple program to sound each speakers for the specified amount of time each time the input putton is pressed. Think of this as turning on a led for about a half second then turning it off and repeating for 3 other leds, when a button is pressed. There are plently of example of how to do that. Once you do that you will find you can easily add another input button and play a different tune. Then you can add a rotary selection knob and build multiple tunes. Add addtional relays and you can flash some lights when the horn sounds.

I had concerns that the traces were on the thin side as noted earlier but I still think you can rearrange parts and small traces, and widen the power traces to use 1oz copper. The overall placement is pretty good as the power traces are nearly a straight line on the left side of the board.

Well it will be their loss, because that it a handy reference that many will find helpful.

Thanks, a handy reference. How about Advanced Circuits, www.4pcb.com?

xwasx, I don't see the benefit in adding a bunch of parts (LM317, LM337 and resistors necessary to set the voltage) to increase the precision of the upper and lower rails of the op-amps when most of the PS's life will be well within those ranges . It seems controlling the voltage to the non-inverting pins of U2 and U3 would be more critical and would provide bang for the buck. In this area you are utilizing a 6.2 and 3.3 Zener to get 9.5V. Why aren't you using 2- 5.6v zeners which are less affected by temperature change than the 3.3V zener or one part- a 7812. If you have to have a negative rail of approx -4 then why not use a single 3.3 zener here similar to the 5.6 in the original design? Because you are only supplying 9.5v to U2, you had to increase the gain in U2 from about 2.6 to about 3.5. As you increase the gain, the op-amp becomes more sensitive to change in your opamp inputs resulting in diminishing returns. In the end are you really ending up with a meaningful improvement with the LM317 and 337?

liquibyte, glad you got it going! You have limited parts with Eagle, so it happens that you grab a device that has reversed leads from your actual part.

I'm a little confused on what is real and what is simulated.

Yes, the price seems out of line with other board manufactures. Your boards looks good enough and it is hard to make them yourself for that price! I actually made an order from them for a simple rectifier board, similar to what you would use for your Radio Shack transformer. I'm waiting for them to arrive. As for your LED always being on, check your transistor Q3 to make sure it is connected properly. You could have leads crossed. Post the voltage reading of all of the pins on U3. Check to make sure you didn't swap R19 and R20.

Make sure you don't have a bad potentiomenter (R2). Check its value during the events to see if this is stable.

xwasx, What is the capacity of your transformer? 2.5 A is a healthy load. I'm curious about the effects when the current is lower. Do you have a sketch of how you set up option 4) bf256 + zener6v2 + zener3v3. It seems you measuring output of the PS but what was happening at the output of the different voltage references?

Liquibyte, your board looks good. The only thing that stands out it your OUT+ and OUT - header is very close to the mounting hole. I think there if enough room to miss the mounting bolt but if you are stacking board is may be more difficult to make connections once installed. I probably would have either moved the terminal block between the first 2 headers on the upper right side of the board, or just soldered an additional wire to the emitter on the 2N3055 (after the 0.33 ohm resistors) and solder an additional wire to the 0.47 ohm Sense Resistor and those 2 wires would serve as the main power carrying wires for the PS front panel, whereas the OUT+- pins can be used for testing/Misc but you wouldn't need to carry 3-5 amps through your board. I guess stacking the boards back to back is a possibility. If you end up doing a lot of assembly and disassembly/testing I would suggest using a push on type connector (such as molex KK with a ramp) for the voltage and current adjustment potentiometers) These carry very little current . Assembly, testing and disassembly is quick and easy because you don't need to figure out which wire goes where - the ramp only goes one way. Also if you have stacked boards you can use a right angle connector and won't need a tool to remove. Again these are really incidental comments .

Hi GoodmanMotor, you are asking such a basic question that I don't think anyone is going respond becasue there is just too much information already at your fingertips by typing "What is a transistor" "How does a transistor work". There are ton of resources from Wikipedia to Youtube. Why would someone retype that general information if it is already available. If you have a specific question you may get a response.

There are many economical switching power supplies units for sale but I had difficulty finding any complete designs (None in the Projects section) with proven results. I know there are some disadvantages compared to a linear supply but many of the advertised units have reasonable performance specs although the quality of parts may be questionable. There are also some advantages as well. It would be nice to have one for this forum to discuss/improve. Anyone with a design?

Liquibyte, Are you using EAGLE? I would suggest shrinking the outline because most fabricators charge by the outer dimension. The price is likely for a minimum of 10 boards at $20 each. $200 total. Better verify.

Do you intend to have the board professionally made? Some board houses require a minimum of 3 boards (OSH Park)and you pay by the area. If you only need 2 boards, than you may want to make single boards and have one spare. All of the traces are the same size. My preference would be to use small traces for the millivolt powered parts which are 90% of the parts and use double the size shown for the power traces. For example, you have conveniently located IN+ and 2N3055 Collector very close. I would have doubled the size of that trace. Between IN- and R7 I would have done the same and then from R7 to the output. The only other item that has some power is the CE pins of the BD139 but your traces look adequate for that.