Virus

MP Thanks, makes sence if you dip it into flux first. Virus

audioguru I was wondering why it is recommended to use

Allvol Enjoy tee, remember still need a answer on this side. Luckily, accumulatively, on this forum there is a couple of years worth of experience. Awaiting your solutions and advices. Virus

Allvol I had a ball playing with the fan’s. Did the 10k trim pot as per your diagram fan1.gif, works excellent, can get the fans down to just- just- just- turning (long pulses). I also left the other trim pot in place, between the 2 pot’s and changing the cap C2 with different values, what a range?, with some setting nice (annoying) music on the fans ! I have a question though, how much of what, here, will do the trick? This project started out with resistors and a dip switch, because of the circuit in

MP I believe it is just a small steel holder with some solder in it ? Doesn't it leave a like droplet shape at the end of the wire?, making it difficult to put trough a hole? Virus

Arup Yep, normally under my nose. ;D Thanx Virus

Hi P1 is the 555 circuit of audioguru and measured on my MM. (Was running the fans etc.) P2 is the “textbook version” of allvoll and as measured after replacing the 47uF cap with a .47uF cap. My MM does not read if it is to slow. Yes, I did get the LED to flash, with the 47 uF cap. As mentioned before both circuits are working. The original 555 with the opamp and the 2 transistor, and the audioguru version are working. The fans are running OK. Now lets get the range with the thermistor in place, where to from here? Thanx Virus

arup I tried the web seams like "Stripboard magic" is not that easily available, would you be able to send it to me. Virus

MP Do you have a photo or a link of a solder pot. Could maybe be more descriptive. Thanx Virus

Dazza Sorry for being so nosey, seams like all the other guys know, no one asked, what is the “…hydrogen project, for the construction of the reactor chamber.” for, this could be dangerous stuff, right ? Just for interest sake. Virus

Guys I HAVE FOUND THE PROBLEM, I had the Mosfets supply and drian short-circuited on the breadboard as soon as the circuit switches on. DEAD SHORT INSTANT HEAT. With that sorted out I have successfully built the circuit in post number 19 (with the MC34071 opamp) and the one in number 34 audioguru’s circuit. I choose for now to go with the audioguru’s circuit, with less components, and is still on the board. As I got the same results from both circuits. I have replaced the 4.7k resistor with a 1k resistor, the fans where making a very lousy high pitch sound, then measured with my MM, I get 21kHz, on pin 6 of the 555. First I replaced R5 with a 10K resistor (because the thermistors value is changing and need a fix value to work from), and adjusted RDC to give an output of 4.5 volts, with the fans just start turning. Then I replaced R5 with the 10 k thermistor, the output voltage varies with MC34071-D.pdf

allvol I like say it, "If you are right you are right.", sorry for ignoring you.

audioguru Thanks for the circuit update, will build it this weekend and give you feed back. What should the value of D1 be ? ??? I will bug you a bit more later, I would like to get rid of the RDC 10K and rather use a solid resistor, with a 10 K thermistor, iaw, make it a circuit with a solid predetermined value for the temp sensor to react on. Thanks Virus :D

I only had the led connected, no fans at all, wanted to see if the circuit at least is working. Resistor RF = 90Kohm Yes, for the 555, I can hear it load enough. I use the 0 - 30 VDC power supply from this forum, it does not even blink. audioguru, is the theory of this circuit good ???, regarding the post of allvol

audioguru I have built the unit (Reply #19 on: May 12, 2006, 05:44:34 PM ) on a breadboard, 1 ste time not lucky. The mosfet gets steaming hot instantly, if I clip + 12v to the circuit, with no out put to the led that I connected. I can hear the 555 oscillating. How can I test the opamp to see of it is working. I have checked and again checked and again checked and …. the wiring can’t find the fault. Should I rip it all up and redo it? Build it to a PCB ? Attached photos. Please help. Thanks Virus

audioguru Thanx will build one and give feed back. Still no idea on the resistor and the selector thingy. Any ideas ? Thank you Virus

Guys Sorry I did not notice the connection in circuit3 posted above where missing, my mistake. Question still remain, where do I connect the thermistor, in the circuit 3, or in circuit forum lab 3, above ? ? ? ? ?. which ever is the better or more reliable of the two. I do have some 10k thermistors can I use them? Re: the two resistors in parallel – this site where the circuits come from, on page http://casemods.pointofnoreturn.org/pwm/741.html In the 2nd line he states – “using a rotary encoder to set your resistance.” Does any one have an idea how to use an encoder switch to select resistance, (This could be the answer to the original question) Thanks once more. Virus PS: audioguru, can you please explain to me how to use the "quote" section. Do you select a section you want to use and then hit "Quote", or how?

AllVol 2 Questions, please I am very greatfull for the help. 1. Where do I connect a thermistor to this circuit, to regulate the fans? 2. Why would the circuit I posted, from this site not work? Thanks Virus ??? ??? ???

Audioguru I have find a circuit at a quite informative site, http://casemods.pointofnoreturn.org/pwm/index.html and have attached the diagram, could you please indicate where I should attache the thermistor in this circuit? Also I have 10 K ohm termistors, could they be used? Can their be any enhancement made to the circuit. ? Again all the questions. Thanx Virus

Thanks Will have a look see Virus

Audioguru Again a eye opener from your side ! ! ! Just one question, if I opt to go with the resistors and the dip switch switching the resistors 1 at a time, what will happen if for example 2 switches are on at the same time ? Would a PWM circuit use much less heat. And how would I incorporate the thermistor to do the temperature control ? Can this exciting circuit be modified to do just that ? Sorry for all the questions but if PWM is better can you help me with it. Thanks Virus

Hi Guy

Zeppelin The whole though was that dip switches would be the easiest, but then the problem with the parallel resistor etc. Unless one starts with a higher value resistor? audioguru It’s the same circuit we discussed before with the thermistor emulation, I now put the thermistor with a air gap just above a lamp, as the lamp heats up the thermistor causes the fans to pickup speed, the airflow cools the thermistor, going up and down etc. and it is working fine. Haven got the full spectrum of min and max but is doing ok. Attached circuit as requested. Is their no other way to pre-select the resistor values in this circuit. Thanx Virus

Hi guys I found these switch on the web. Think they will do it ? Your ideas please. Thanks Virus R_1apr.pdf

AJB2K3 Any suggestion that I can look into. Thanks Virus