So i was having trouble the other day with a circuit I was testing and my oscilloscope going bonkers. I did not know what was going on, so I did some investigating and low and behold my homebrew power supply was acting up and had massive amounts of noise and ripple on all the power rails. So i grabbed a couple of these off ebay cheep, thinking well if they are crap i will send them back. Checked the ripple on the output and its not bad at about 100mv, not the greatest, but not bad enough to cause the scope to act up. Time will tell how they go. About the only thing I really need is a 3rd channel. I often need to run 2 12v rails and a 5v. So im going to have to hack up some dual leads. I went looking for double adaptors with 4mm banana and dual terminals, but they just don’t exist anywhere i can find anyway LOL
I am no fan of desoldering, so when i saw this tool on ebay i was skeptical that it would perform any good. So i gave it a whirl today to see if it was going back or staying. Well its staying, its actually pretty damn good. Its not cheep for Chinese crap but it does the job. Nozzle over a pin, wait a second or 2 for the solder to melt, hit the button and suck it out.
Putting the Doo back in Doohickey. I bought a new function gen, but this one is much fancier. Its like the licorice all sorts of function gens, does AM FM, PSK some things i have never heard of and well as Sin, Square, Triangles of various types and other kinds of squiggles. Seems to work well enough.
So i sat here this morning with a bag of 50 crystals playing a game of what is the resonant frequency. Thoroughly boring I can assure you and I am not sure how the ladies at uBitx Labs in India can sort through thousands to get sets of 8. But alas I have done enough for now to get 2 sets that are matched at a guess to within 50hz, being that my frequency counter is only good to 100hz.
One thing that I would not have predicted is the distribution in the resonant frequencies. Its like buck shot, all over the place and the other thing I would not have predicted is the number of dead crystals or ones with so low Q they might as well be dead being 8, that seems like a very high death rate to me. I still have 2 more bags to sort, but thats not happening today, i have 16 matched crystals I need for 2 filters and am moving on to the next thing.
Need a tool, make a tool as they say. Well i need to sort these 100’s of xtals into groups of similar frequency for use in xtal filters for an upcoming homebrew receiver project I have started. I have like 200 12mhz to sort through, so i should be good for a few filters at least. Its just a matter now i sitting here for a few hours and sort them all. Not looking forward to that. 🙂
No rocket surgery here, just your basic oscillator and buffer circuit that can be found all over the internet. Its simple, it works and it is reliable.
Built it up Manhattan style on a scrap of copper clad pcb. Yeah i love MeSquares to all you MeSquare fan boys out there. LOL
The Joy Of Oscillation, it works. 3 xtals checked, 100’s left to go.
Just A Bunch Of PSU Modules?
All good projects need a name don’t they? Sadly I think just a bunch of modules has been taken by Pete Juliano for one of his many radio projects. Oh well, such is life. I was thinking Buck This or Well Switched or Ebay Wonder might also do. Anyway, i have now completed the project. It has its lid on and it works. Here are the final images, a couple of them are even hi-res using the SLR and not my mobile.
Here is one of those Tribal Knowledge moments that we often hear about. This is 6 core shielded computer cable, I used it to wire up the pots. It helps keep things nice and neat.
It worked out quite ok, next time I will spend some more time measuring then cutting just to the right size.
I do not like playing with mains voltage or anything that can kill you. It is why i went for a modular option, so that when I am done there is no exposed 240v anywhere inside the case that dummy hear can touch while doing da-finger-poken inside the case. Not that the lid will come off hardly every, i just am very cautious of anything that can kill me.
Here i have started to wire up the DC power side of things. I am not all that much of a neat freak like my friend Simon 6MSC, who can make toriod winding look like an art form, but I am trying to keep things somewhat tidy.
Now we are getting into the meat of it, things are all wired up and zippy tied all over the place.
An overhead shot of the whole guts of it.
Now i do not pretend to be a metal worker. I was really happy with the bottom half of the case. But, alas i turned the top half into an abortion. First off i folded the metal on the wrong side of the line and made it to narrow so that it would not fit properly. So I had to try and fold it flat and start again. Sure i could have scrapped it and started over, but hey, why waste such a large sheet of metal. So i folded it a 2nd time, this time it fit, but one side is 5mm short. I can live with that. I know that the next time i make a case, which will not be all that far away, will be much neater now that I know what I am doing. Thanks for reading, hope you enjoyed the project.
So i got in and did a bit more work on the lab power supply. Finished off marking out and drilling every hole for every component so i do not have to go back and make a mess inside when i start to wire things up. Other than 2 tie bars across the top, the lower half of the case was done in the image below.
Mounted the switch mode PSU into the case, its held in with 4 M5 bolts and is not going anywhere, the fused, switched power connector and EMI filter are also bolted in with M5 bolts. The earth wire will be bolted to the case also with M5 bolts as well as serrated washers, so it cannot go anywhere. Go over the top on safety is my motto.
Mounted all the front panel items. From here its now just a matter of wiring up the spaghetti and making it all work together. But that will be another day, i do not think i have any wire suitable for 240v ATM and will need to go and get a meter of 3 core to pull apart for the internal wiring.
I have not had much luck with the inductance setting on LCR meters. Most of them are crap, inaccurate and just plane useless. I think this is the 5th cheapish meter I have tried and I have finally hit on one that works and works well. In the picture below is a 1.8uH slug tuned variable inductor. So yes, it works and is accurate and with 3 decimal places its going to be nice to use for getting those hand wound toriod inductors right. The test frequency is a bit low, it would be nice if it was in the MHZ range rather than KHZ, but for that you need to spend up big on high end gear, not $70 on ebay.