Kain

Well, to be honest it never even started working on first place. I changed the chip once too and guess what - no change at all. I do not think I have overheated the part either - the soldering was really quick ::)

Fantastic... So, besides calling 911 what can I do to make this thing actually work, or any other suggestion?

Ok, here is a quick drawing of what I was thinking about. I was thinking about current limiting resistor in the collector, but I have the feeling I will be cooking my dinner on it...

Oh, and by the way, I am trying to use this switch stright from 110VDC...

Recently I had to use some 12V electrical clutches that draw about 4A continuosly under operation. I wondered if I can make a simple 1 transistor switch that can take this whole load? I was thinking of common collector configuration with zener stabilizator in the base. I do not care of any ripple since it is just a clutch so let it get as much noise as it wants

Hum... Am i supposed to solder those with low voltage soldering iron?

I just tried it - doesn't help at all. You ment the capacitor to be between the input and ground, correct? I used 1000uF cap to try it ???

Congratulations for the 3000 posts (already 3004). Is there going to be a party too? ;D About the step-up PSU - i tried setting the current limiter to 350mA and yet exactly the same as before happens. Sometimes actually the board fires up, BUT I am unable to regulate the output trough the trimpot while I am actually supposed to be able. The output simply stayed at 4.65 - 4.7V which is even lower than the input... I really hate when something doesn't work

I have been trying to build a low power step up PSU for my PIC programmer. It is supposed to take 5V DC and convert it into 20VDC. The load takes about 50mA. I tryed to achieve it with TL499A, and on first sight I think the schematic and the board look good. However, when I built it it seems that something is shorting up - I think the chip is not working properly for some reason. I know that it is shortening because the current protection of my PSU goes on even when i set it to upper limit, such as say 250mA... Circuit.pdf PCB.pdf

Alrighty, I have already built the modified PSU. I haven't done much testing though but I noticed that the maximum voltage was actually 28V instead of 30V. Any idea why this would be? Here are 2 pictures of it assembled ;D

So far I have been using only Protel for my simulation and design purposes, but since now it seems I will be studing Orcad in university I wonder which one can be thought as a better software and if it is why would that be? I know it's all about personal oppinion in most cases but I've never tryed Orcad and all I know about it is that it is less user friendly than Protel (at least users say so). Any oppinion is welcome

Ok, it seems I will have to answer myself. I would take the Tektronix because it does 1Gs/s up to 60MHz on each channel vs. the other one which is capable of only 100Ms/s on each channel. The Tektronix has some additional functions that will come up handy too. Amen

It's been a while for me walking arround and asking to use scopes so I finally decided to buy one, not to mention that I got some cash specifically to buy a scope. Now, the 2 models that I looked at and that I can afford (digital ones) are the Tektronix TDS210 Digital Oscilloscope and Instek GDS-806S 60MHz Digital Storage Oscilloscope. I know that Tektronix is pretty good company indeed, but sometimes they tend to be quite pricy. Those 2 scopes I could buy on the same price - $650, but i don't know which one i should choose. What would you advise me? And please, tell me why I would choose one instead of the other? In other words I need to know the advantages and disadvantages of each model.

Ok, finally some late update on this project. I assembled the dual layer PCB today - as expected it's really compact and neat

Yey! Finally back in ;D. I can't believe I survived those hours without the site running. It's still slow though. Maybe it's not over yet? ???

Alrighty, I will try to attach an antena to SW1 somehow and hope this will do it. On touch actually it does make a huge difference, I mean when I touch SW1. Thanks anyways. :)

Audioguru, you are right in general but the things change when you decide to use high intensity white LEDs or high intensity LEDs in general. I have about 100 of those still left over with 20000mCD intensity, and about 10 more with 13lm flux. When you actually overdrive the 20000mCD ones on 100mA vs. 25 which is the nominal they do look way brighter, and when you overdrive the 13lm ones on 450mA vs. 150mA linear they look more like a freaking flash-light than LED ;D. I mean the difference is like day and night. If you try to drive them on even higher current though they start fading out - the crystal overheats, thus they loose their intensity dramatically not to mention the LED is in fact dying. The interesting part is that somewhere on the limit of screwing them over and getting good results you might get more bluish like color due to the higher intensity of the blue spectrum on those, and on lower then nominal currents the appear more yellowish. However, to the eye they look brighter when you overdrive them since it's not fast enough to catch up the pulses. In fact in terms of power they dissipate about the same ammount as before. On regular LED you won't feel this effect much though. Just try it and you might like it ;D. Oh well, I am just saying what I've seen here when I pumped them up :)

Hi Inspar8r, welcome to this forum. I have done what you are trying to do with the PWM and I used exactly 555 timer. The timing components you can calculate very easily. You can either look up in google for 555 timer datasheet since they will provide you with all the information on the different functions and timings (monostable, astable, duty cycle..bla bla). However, the easier way is just to get the 555 designer which will do all the calculation job for you. It's in the software section in this site. It is that simple ;). Now, there is a problem with your driving circuit though. You said you want to drive 48 LEDs. Well this is very nice but if you calculate the voltage of those when you connect them in series it will be 14V/48 = 0.29V, in other words they won't even feel it. I assume you have been connecting them in groups of say 3 or 4 with current limiting resistor which is good, but the problem will be if you want to hook them all up to the same timing 555. You see, 555 will not take more than 200mA in the best case ever. Actually I am not sure if it can source this much, I believe it can only provide impulses for given time before overheating. In your case driving them at say 60mA will put a load of about little less then 1A, thus if you want to do this then you need to drive a transistor which will be driving the LED matrix itself. Hope that helps. 8)

Oh, I forgot to post the pictures of the adapter. It seems this small rounded component is the antena it is having right now. The wireless controller is obviously the ZyDAS ZD1211 on which I can't find any detailed documentation such as suggested schematics, but this is not that important for now.

I got myself a wireless G USB adapter. Reason why I wanted USB one is because it can be used pretty much on any PC - notebook or desktop vs. PCI or PCMCIA cards which are restricted to either desktop or notebook. Anyways, as expected USB adapters sacrifice something because of their compact design - high gain antena which actually is major pain in my neck. When only surfing the net actually it's ok, but once I become say a file transfer within the local area the transfer speed just falls....it's not even funny how much it falls... sometimes to even 5mbps which is just rediculus. Then, I opened the adapter and touched the device while transfering - there we go crusing back to high speed. If I remove my hand it goes back to snail crusing speeds... It is obviously lacking the benefit of having a better antena (in fact i can hardly see anything that can be called antena in this thing). I wonder if there is a way to make small if possible PCB high gain antena, or at least higher gain than what it currently has? I'm willing to construct new case for this too - the original looks like crap ;D We are talking about frequencies in the range of 2GHz by the way.

I did some timers recently. I highly recommend you CMOS 4538. This thing is really accurate given you have good accurate RC, meaning within good tollerance. The C has no limit and R can be up to 1M Ohm and the formula to determine the timing interval is T=RC. This is more than simple. The chip consists of 2 independant resetable/restartable/non-restartable monovibrators that can be triggered independently, there u get 2 timers in one chip ;D. Since you were talking about CMOS chips from the beginning, just wanted to give you a hint - power your project on 12V, or anything between 7.5 and 15V. The reason why I am saying it is so it will be noise imune. You can see the thread about the problems I had before with CMOS on: http://www.electronics-lab.com/forum/index.php?board=2;action=display;threadid=2656 CMOS is fairly easy to work with once you get what you are doing wrong ;)

Ok, here is the big no no I did on the PCB - I have traces passing between the pins of the ICs... Don't comment me pls ;D. The other thing is that some of the traces (I just didn't want to say all :-[) are pretty long for CMOS based circuit. And the really big no no was powering them up at 5V in the presense of industrial noise. At this voltage the noise to signal ratio is just bad (according to what I read 2 days ago). I tryed now the same thing at 12V and they worked nicely. Here is the PCB so you can see my major screw ups ... Who said that it's time to redo the board ? ;D

Hello, recently I did some CMOS timer design and it was working fine until we tested it in combination with some other relays. When we did this it started bouncing like crazy, so I think it is typical example of industrial noise influence :-[. Now I tryed to deal with it by putting optocouplers in the trigering inputs. Well it didn't even come close to solving it... You can see on the chematics that the power supply separates them from the AC. Maybe I need some additional filtering against high frequency noise (using inductance) or so. Am I missing something in the overall, such as some input floating and picking up noise? ???

Yea, I dunno what was wrong with me. I found 10000uF/63V for 5$ each at mouser, so total is going to be 25$ which is acceptable ;D. About the transformer I don't recall saying it costs 10$. I would really like if it was 10$ though....hehe. The one I am getting will be hammond 30V @7.5A for about 50$. Hopefully this will do it 8). About the ICs I mentioned earlier that you should order them as samples from Texas Instruments as I did. I already have them too. This saved me little more than 25$ per board (since my PSU is dual output) ;D

I was just collecting the parts for this project and the price of C1 almost killed me - it costs as much as the transformer... Do you think I can use the same value capacitor on 50V instead of 63V, since it's almost half cheaper then the 63V one? Or maybe somebody knows a place where I don't have to pay $40 for a cap of this value. I was thinking to wire up few smaller ones in parallel but guess what - it comes on even higher price... :(