Kain

Yes, this is exactly what I ment. For a second I though that something is wrong with me too. I mean, I saw that somebody said that the emmiter of Q1 should be connected to ground and since it is already shown correctly on the schematic that you posted I wondered what the heck is wrong... ;D

Ok, I know this is not one of my smartest questions, but where the heck is the ground - 0V of this PSU? ;D

Thanks Ante. I was thinking to buy the chips but when I saw the price my mind was more like "HELL NO!!" However, when I saw the chip manufactor my mind changed to "wait a second.... " ;D I'm thinking to redo the PCB on Protel taking the rectifier and Q2 off the board. I am also planning to do some vertical resistor mounting since it saves space. However, this will happen after I get all my parts 8). By the way, does Q1 need a radiator as well or it can go without having one?

I've been following this thread for quite a while since I built the original PSU 0-30V / 0-3A and still don't have any major problems. The reason I don't have problems though is due to the fact I never use it on its extremas. Now, I plan on modding it up to 5A with all the changes you guys suggested here. The most expensive parts however seem to be the OPA445AP. I didn't find them online any cheaper than 8$/piece. However, I found they are made by Texas Instruments. Therefore, if anybody is interested in building the modified version, just go and order samples from www.ti.com - you will save about $24. You can order up to 5 chips from each type with the limit of 8 different types. Oh, and you can order more than once ;D. I just did and wanted to share with you guys. The people from http://www.electronics-lab.com/forum/index.php?board=21;action=display;threadid=21 know exactly what I am talking about, right guys ? ;D

Yes, you cannot exceed the power rating of the pointer, unless you change the swithing mode and so on, which means that the intensity of the source remains const.

Quantum, focusing the source does not increase its intensity at all on first place. It's the same to say that just that you put a lenses in front of your lamp it makes it more powerful (since power increases with the intensity doing the same). The intensity of your source will remain the same unless you use more than one source. Semiconductor LASERs work in switching mode usually - there is an integrated small circuit on the board that is some sort of impulse generator (multivibrator or so...). I have read some time ago that the output intensity of the LASER LED can be increased dramatically with appropriate switching and higher input current. This however, causes it to live shorter due to the increased temperature on the PN junction. Focusing the light increases the intensity on given area. However, in your case the LASER LED is already focused by the built in the pointer lense - this is why it's beam shaped. I doubt you can focus it better than it already is. ::)

Well, according to the original source you are supposed to buy those since no information is given on how to make them or more specific data, such as inductance...so on. By the way, see this: http://www.rfparts.com/choke.html

Quantum, mCd stands for microcandela - unit for light intensity. I guess the "m" should look little different for micro, but we are limited by the software :). Cool about the pointer. It better work too ;D

Input voltage does not affect the wavelength of any monochromic light emitting devices. What it could possibly affect is the intensity, but nothing more. Some laser pointers are rated between 630~670nm meaning it COULD do the job for ya. If you can emmit a regular white light you will have pretty much the full spectrum of wavelengths, thus the one that you need as well. There are fairly powerfull white LED that are nothing else but 3 LED sharing the same package - RGB (colors). I have seen this type of LEDs with 20000mCd intensity which is, oh well, enough to cause demage to your eyes. If you can focus this into a nice concentrated beam...you might be able to have fun with no lights on ;D. I personally have tried 10000mCd - it is a lot....especially for a LED 8).

Quantum, the other street light doesn't turn those off because the sensors have a limited scope of vision probably as I said before. They simply don't get exposed to any light from the other lamps (as we all know light follows only stright path). About the UV sensitivity, sensors are usually not built for UV sensitivity only. However, the selection of a single wavelength is fairly simple - they only need one plastic filter in front and voila - there they have it UV sensitive only ;D. I don't believe they use this technique though because the limited scope of vision is more than enough for this trigering to work.

Ante, I've been using this solution, but it works only if you can deassemble the used transformer ;D

The LASER light wave-length is more based on the chemical properties that on junctions. There might be UV LASERs, but keep in mind any LASER different than red color 630 -680nm up to 5mW is very expensive, meaning any other light different than red on LASER is expensive on first place. The other thing is that this beam has to be perfectly illuminating the sensor. What I mean is that LASERs are focused into a tiny beam meaning that the illuminated area is small. The other problem if you use LASER is that UV as you know is invisible for your eyes, thus this makes it extremely hard to allign the beam without equipment. The most important thing is that you don't know if the sensor is particularly sensitive to UV only - it is only a guess. If it's not sensitive to UV only, then you can use any focused beam from light with the same sucess :).

By double hetrojunction laser do you reffer to 2 semiconductor LASER in one body? I didn't say there are not UV lasers - there might be but this is not the point. You will need direct exposure to this light of yours to make the lights turn off. If the sensor is on the top of the lamp, it probably has limiter scope of vision which is simply a tube and the sensor is inside. This way only light at seciffic angle can get in and trigger it. Say in your case they use a cone for the tube - they will have wide enough angle to cover the whole day, but for the lights still to work night time.

I had similar problem, but mine was with fluctuation of the panel all over. My solution was to power up the pannel on bipolar, i.e. +-5V with midpoint. I suppose your panels allow you to connect them this way, or hopefully they do. The good thing is that you only need few miliampers to power up the thingy. What I did is I used two zeners at 5.1V with resistors, and built basically the analogue scheme of voltage devider, but instead of 4 resistors, I used 2 resistors and 2 zeners. Zeners are connected together in series the resistors are connected again in series - one attached to each zenner. The midpoint between the zenners you can take as zero - it will be relative zero, so between the midpoint and the other pin of the zeners you will have relatively +5.1 and -5.1. The good thing is that you can take the power to power up the zener stabilizators from the rectifier bridge of the PSU, meaning no more transformers in the case. Resistor values will depend on the potential input - use ohm's law. This worked for me and hopefully it will work for you :)

Well, particle generator I can think of is only LASER. However, this sounds kind of pointless, right? I mean instead of dealing with laser you can basically turn some lamp on and it will do it ;D. It's true that laser light and regular light are waaay different. LASER is coherent, focused, monochromic.....bla bla, and regular light is a mixture of pretty much any colors. My guess is that this photocell has some filter on it for speciffic light - probably UV since many lamps are filtered from UV light;otherwise it's located somewhere where the lamps themselves cannot illuminate it. In any case you will probably have to climb to illuminate the sensor ;D

Cdonke, if you know the purpose of this inductor in the circuit you will be able to calculate its inductance as well. It's probably a filter by the way. Actually I just checked - it's a filter yes. Notice that you have the same LC filter on the input and output. It is put there to cut frequencies in the specified region I guess. Just try your best to make the coils as similar as possible.

Light has both electromagnetic wave characteristics, but has particle characteristics as well. So, if you think about it, what you are trying to do is basically affect a photocell to switch only based on waves, which will deffinately not work. Photoelectric effect is not based on the wave nature of light on first place - it is based on the particle nature of light. You should know this better than me Quantum ;D. Just kidding :). Unfortunately, you will still have to watch those lights working night time. By the way, only for information, light wave-length is in the nm region... Just calculate the frequency related to this wave-length, and think if it's possible to build this radio-wave transmitter even if this switching was about to work ;)

Cdonke, I assume you are trying to build some radio transmitter. The formula that Quantum gives you is approximation by the way that sometimes works sometimes not (for me it did and didn't as well), and it is for single layer coil, meaning that you cannot do (you can but the error will be greater) calculation for multiple layer coils. I advise you to follow the instructions on the schematic you are trying to build. Inductance cannot be replaced by resistor in general, but it depends what is the role of this inductor in the circuit you are using. A coil can be used to filter certain frequencies, for example, thus it works as resistor in some circuits, but notice a regular resistor limits all current no matter of frequency; so you see it depends on the circuit you are using. The distance between the turns affects the inductance - higher distance results on lower inductance. If they say nothing about spacing between the turns, assume it's 0. What is the circuit that you are building though?

Dazza, what kind of panel metters do you use on first place? Can you upload the schematic that you use to wire them up - I mean their power supply - dipolar +-5V or single 9V, or whatever it is? I use panel meters too, and I power up everything from the same transformer that I use for the PSU itself - probably what you want to do too since this will automatically kill the reason to have extra trasformer in the case :).

Ok, I managed to fix it finally. The solution was as I suspected - common ground. I used the same transformer as for the PSU and made zener stabilized +-5V with mid point output, and I filtered the output potential with 1000mF/25V cap. Now it works absolutely stable - the measured value does't fluctuate even for one digit. ;D

Ante, I already tried this, and just to make sure I did it once again with no improvement. I tried cap in the iput before the voltage devider as well as after the devider - no change at all. I wonder how the unit would work if I hook it up in the other way - I mean powered by +-5V. I see it has a common ground with the inputs which might turn out to be the solution. What do you think about it? ???

Ok, now I got really weird problem. As I posted earlier in this forum: http://www.electronics-lab.com/forum/index.php?board=2;action=display;threadid=128;start=120 I'm trying to use digital panel meters for this PSU project. Everything seemed to be alright untill I tried to measure voltage from any power supply. What I mean is that these digital panels work fine when I measure potential from a battery, for example. However, once I hook it up to transformer based PSU it freaks out - it shows bogus numbers that fluctuate all over the scale. The weird thing is that even if I don't hook it up the voltmeter starts fluctuating a little bit. I powered up the panel as shown on the diagram by 9V battery. Any idea what could possibly cause this? ???

You are very welcome. What do you plan to do with this thing of yours, besides breaking it? ;D Just kidding though - I'm judging by my actions probly hehe 8)

Hum, I don't think it's cap what you are looking at... I just don't picture cap marking with R ???.... looks as non-sence to me. However, SMD stands for Surface Mount Device, or in "english" ;D it means that there are no holes in the PCB in order for the element to be mounted, soldered....whatever you want it. This is why it's called Surface Mount - because it is mounted on the surface of the given layer. :)

Hum, I don't know what to say now haha. There are too many small black things going arround on PCB. May be it's SMD resistor? ???