beginner project - what can I do with these crystals? - Page 1
Forum section: electronics / beginners

author: dentaku
author_rank: Frequent Contributor
timestamp: May 25, 2014, 07:48:03 pm
content: I salvaged 12 crystals from an old Midland 13-882B CB radio. They all labeled either 5L4 TEW or 5M1 TEW.I've never done anything with crystals before I would like to build something simple with one just to learn more about them.What could I build to test them out and actually see something on my old 60MHz Hameg scope?I found a list of all the frequencies of all the channels and how 12 crystals can give you 23 channels.

author: jamesglanville
author_rank: Contributor
timestamp: May 25, 2014, 08:18:29 pm
content: If you want to get them to oscillate, you can use a inverter gate to make an LC oscillator:http://1.bp.blogspot.com/-mAmLljbgTAY/Tn7WVO2MNgI/AAAAAAAAA3g/7xNOq1-c-AU/s1600/pierce-osc-cmos-inverter.pngYou can use any inverter, NAND or NOR chip you may have lying around.

author: w2aew
author_rank: Super Contributor
timestamp: May 26, 2014, 12:13:03 am
content: Here's a simple crystal oscillator project you can build

author: dentaku
author_rank: Frequent Contributor
timestamp: May 26, 2014, 01:01:23 am
content: I found this article earlier today before posting this questionhttp://www.crystek.com/documents/appnotes/Pierce-GateIntroduction.pdfI have some 74c14 Schmitt Triggers so I'm assuming that would work even at those frequencies (well... it sounds high for a person like me who only messes with audio).I guess all I can do is try.Quote from: jamesglanville on May 25, 2014, 08:18:29 pm

author: dentaku
author_rank: Frequent Contributor
timestamp: May 26, 2014, 01:20:53 am
content: You know, I've watched that video before but I was more interested in the island cutting method than the circuit itself.Now I've watched it again and learned even more.By the way Alan, you must have a steady hand and good image stabilization because your handheld videos barely shake at all.Quote from: w2aew on May 26, 2014, 12:13:03 am

author: corrado33
author_rank: Frequent Contributor
timestamp: May 26, 2014, 05:16:50 am
content: Quote from: w2aew on May 26, 2014, 12:13:03 amAlso liked the island prototyping idea! Definitely want to do that now. Fun little circuit!

author: M0BSW
author_rank: Frequent Contributor
timestamp: May 26, 2014, 09:59:06 am
content: Quote from: corrado33 on May 26, 2014, 05:16:50 amYou should build this it's really easy ,and useful too.

author: dentaku
author_rank: Frequent Contributor
timestamp: May 26, 2014, 10:49:01 am
content: I'm going to breadboard W2AEW's crystal tester when I get back from work.if I've still got the energy to mess with tiny thingsQuote from: M0BSW on May 26, 2014, 09:59:06 am

author: dentaku
author_rank: Frequent Contributor
timestamp: May 26, 2014, 08:52:43 pm
content: Well, W2AEW's circuit works as a Spice simulation.Now I just have to build it for real.

author: retrolefty
author_rank: Super Contributor
timestamp: May 26, 2014, 08:56:28 pm
content: Build a ladder crystal filter:http://en.wikipedia.org/wiki/Crystal_filter

author: dentaku
author_rank: Frequent Contributor
timestamp: May 26, 2014, 11:38:29 pm
content: Well, at first I wasn't sure if it was working because lots of those old CB radio crystals were around 8MHz but I found a few that measured at roughly the frequencies the table I found said they should be.SO... I found another old crystal I unsoldered a long time ago and it measures at around 3.5MHz so I looked at the case of the crystal and it says 3.600 so I'm guessing the circuit worksMaybe someday I'll have a use for crystals but at the moment it's just an educational experiment.Some of them put out weird looking signals and others are decently sinusoidal.Quote from: w2aew on May 26, 2014, 12:13:03 am

author: deth502
author_rank: Frequent Contributor
timestamp: May 27, 2014, 12:05:56 am
content: Quote from: w2aew on May 26, 2014, 12:13:03 amthis was the first thinig i thought of when i read the op. i built one myself. very easy, very useful. it has definitely earned a place in my tool box. i dont have the fancy cutter, but hoging out a few squares with a dremmel tool works just as well.now while we are on the subject of learning.....in addition to different wave forms, as you posted, i have noticed widely different swings in amplitude between different xtals as well. with w2aew's circuit, some would put out barely 1v p/p signals, while others would be up to the 9v supply voltage.

author: dentaku
author_rank: Frequent Contributor
timestamp: May 27, 2014, 01:54:18 am
content: This week sanded off the green solder mask from a chunk of circuit board that had no traces on it to see if it was possible to expose the copper without sanding it off too and it worked fine. It REALY stinks and actually reminds me of horse manure (if you've even smelled that).I might try taking this circuit off the breadboard and building one like Alan did by cutting out little islands with a broken drill bit or maybe even cutting oval or rectangular islands by hand with a nice rotary tool I have downstairs then drilling tiny holes in them and placing the components on the other side of the board and soldering them to the copper side the way regular PCBs work.It's a very precise tool, not just a cheap Dremel and I've got some tiny bits.Quote from: deth502 on May 27, 2014, 12:05:56 am

author: dentaku
author_rank: Frequent Contributor
timestamp: May 28, 2014, 12:59:33 am
content: I just decided to pull everything off the breadboard and put it all back together. I think I got something wrong the first time because I'm getting a much nicer waveform now

author: vk6zgo
author_rank: Super Contributor
timestamp: May 28, 2014, 06:20:32 am
content: The ARRL Handbook a few years back showed two uses for a crystal oscillator circuit.One is obviously to test crystals,but by putting a transistor socket on it,you can check that those odd transistors lying around have enough gain at HF to oscillate.A bit of a rough test,but quite useful!