DerFly

Hello my friend, Do a net search on "air mass sensor" and "hot wire" as used for automotive engine management sensors. This should give you a few ideas to research. DF

Yes, not in the projects section. There was a post in one of the forums, can't find it either. I hope someone elso know of it DF

Anderson Power-Poles?

H All, There was a project here detailing the above. Built by a German guy, I think. Beautiful construction with a kind of modular method. The two supplies could be switched together for more voltage. It might have been 0 -15v x2 or similar. PCB artwork was avaulabble and there were quite a few pictures showing the excellent construction. Does anyone remember it? Thanks, DF

MP Thanks, I undestand wiring in series but the variable resistors in this project have three connections. To wire two variable reistors in series, how is this done. Could you possible supply a diagram? Many thanks, DerFly

Hello All, Seems we are all making our modifications to this project. I hope someone can help me with mine. I would like to use two variable resistors each for the adjustment of voltage and current to enable coarse and fine adjustment. The circuit calls for 100k variable resistors. Is it possible someway to wire in 10k variable resistors for the fine adjustment? How does one wire the 100k and 10k variable resistors together? Thanks for any help. A diagram would be great. DerFly. ???

So, I am also building this PSU and have box, panel meters, transformer, etc. I have also finished the circuit board. I am thinking to use a thermistor circuit and 12 volt fan to keep the heatsink cool. Have not decoded to mount the heatsink inside or outside the box yet. I think of two ways to power the fan circuit; 1. Use the rectified 30 volts and a voltage regulator to get 12 volts, or, 2. Use a dedicated 12v 1a transformer with rectifier and filter cap to provide unregulated 12 volt for the fan circuit. What do you think? DerFly.

Mixos, Thanks again. So, I will begin to source the components and begin to build the unit. This will take time (as everything when one has many things to do). I will let you know my experiences. I am thinking that the PN2219 is the same as the 2N2219, only with a different package, so I have a few things to try. DerFly

Mikos, Thanks for your reply! Next question, can I substitute the 2N2219 with a 2N2222? Thanks for your answer to these perhaps very stupid questions. Derfly.

Hello All, I am currently looking for the components to put this project together. It seems that the Op Amp TL081 is not so easy to find in my area. National Semiconductor says that the TL081 can be used to upgrade circuits which use the LM741. Also that the LF411 can be used as a substitute for the TL081. The LM741 is available locally. Can I use thise as a substitute? Thanks for your replies. DerFly Project Link: http://www.electronics-lab.com/projects/power/003/index.html

mozikluv, thanks for the ideas. I already have the 24v 3a transformer, so it is a question of finding a regulator that can handle 3a. I think iI will try the LM338. Do you have any experience with the variable current 30v 3a supply on this site? Think I might try it next. DerFly

Hello All, Just finished building a modification of the following circuit. http://www.uoguelph.ca/~antoon/circ/vps.htm The changes I made were to use a 24v 3a transformer as this was available at the time. I also used an LM350 instead of LM317 as it is rated at 3A. Also used a 2A fuse and some other small component changes due to availablility. The LM350 is a metal can type on a large heat sink. So, the unit works and will power a 12v 10 watt light. The voltage varies nicely under this load and also without load. However, when I try to power a 35 watt halogen light, nothing! I suspect that the LM350 might be cutting out due to current overload. Could this be the problem? Would fitting an LM338 (with 5A rating) be the cure? I originally built this as a general power source for use in cutting foam with a NiCr wire, so think that I will need to draw quite high current. By the way, I am an electronics beginner so any help is greatly appreciated