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 Post subject: Re: Microcontroller Based Signal Generator
PostPosted: Jul Thu 06, 2017 11:05 pm 
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Location: Mesquite NV 89027 (from Coventry, UK)
azenithnut wrote:
This is going to be a very useful piece of equipment!
Lou, thank you for putting all the effort into designing it!

-Steve

I second that!


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 Post subject: Re: Microcontroller Based Signal Generator
PostPosted: Jul Fri 07, 2017 12:23 pm 
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Good to see some results from others. Colin, I see the response from the Emerson 888 is rather poor on the internal display. I had to look up that radio and saw it is a small transistor radio so the output signal must be small. What is the scale on the scope for your photo using the external mode? I expect pretty sensitive. I did not include a gain control on in the input circuit but perhaps maybe I should have. I was thinking strictly of tube radios and an AGC voltage of typically 3 to 6 volts. As I have used the device, if the display maxs out, I decrease the input signal. But no way to amplify the signal for the transistor radios. I may add that to a "model 2" feature list. Also, I do not recommend the "just loop some wire around the antenna" approach. I put the signal through a .1 or .05 cap onto the grid of the mixer tube (6A7, 6SA7, etc). Also, I like to align one stage at a time, starting at the "back end" of the radio. However, there may not be enough signal to get a good response from just the detector IF can.

I am also seeing some hash on my scope from the generator. I thought it was the wall wart but not sure now. I have bypass caps all over this circuit so I am disappointed in the noise. Of course, the case is plastic and not metal as it likely should be. Maybe I can try to wrap it in aluminum foil and ground that to the BNC connector sleeve! Stay classy... UGH.

Also appreciate the nice compliments. I am still trying to use this thing myself and see how often I can use the internal display thus eliminating the need for a scope. I do not think I am there yet in all cases. I aligned an AM/FM Zenith X338 (8H02 chassis) this week and had strange results. The S curve had RF all over it ( ??? ) so the device was not handling that at all. I should post a photo of the scope view. I have not done many FM alignments so not sure what I was doing wrong. I have the SAMS for this and used the proper test point so not sure what is going on. Could be a problem in the radio??? Right now it is working but "sounds funny", i.e. some slight distortion. Not sure if that is the speaker, audio circuit, and something else. More work needed. I know this is a great performer so I want to get it right. If the mystery continues, I will post on the proper forum for consultation.

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 Post subject: Re: Microcontroller Based Signal Generator
PostPosted: Jul Fri 07, 2017 12:34 pm 
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Location: Dayton Ohio
I would suspect that transistor radios will have a different result.

Bipolar transistors are more "current driven" rather than "voltage driven" as tubes are. therefore the AVC "Voltage" may be rather small and harder to scope?

Just throwing thoughts out there.

-Steve

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Consoles and floor models, the bigger, the better!


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 Post subject: Re: Microcontroller Based Signal Generator
PostPosted: Jul Thu 13, 2017 10:16 pm 
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Lou - Sorry for not responding right away. I don't know what the scale was on the 'scope. I had unhooked everything by the time I read your response. I need to try a tube radio and see what results I get, but first I have to obtain an isolation transformer. Used to have one but a severe error in judgment last year means I no longer do.

Steve - You are probably right about the difference between transistors and tubes being significant. Unfortunately, most of my radios are transistor. I was hoping to use the CompuLign on a Zenith TO D7000, when I finally get around to opening it up and recapping it.

I got really cheap when it came to knobs. I ordered four from Tayda Electronics, at $0.49 each plus cheap shipping. Their part number is KN8F. I was ordering more stuff and happened to spot the knobs. They worked for the three pots, but needed modifying for the rotary selector, by cutting off the flange. Not classy, but effective.
Attachment:
Knobs.jpg
Knobs.jpg [ 138.6 KiB | Viewed 2653 times ]


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 Post subject: Re: Microcontroller Based Signal Generator
PostPosted: Sep Sat 23, 2017 12:07 pm 
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It has been awhile since the last post. I was wondering how everyone's project turned out and if you have found this project useful. Any feedback on the operation?

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 Post subject: Re: Microcontroller Based Signal Generator
PostPosted: Sep Sat 23, 2017 12:36 pm 
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Hi Lou,
I haven't had a chance to try it out, as I have not been able to restore or work on a radio in quite a while.
My workbench is inaccessible atm… :oops:

-Steve

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-Zenith
-Sparton
-Pre-War FM
Consoles and floor models, the bigger, the better!


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 Post subject: Re: Microcontroller Based Signal Generator
PostPosted: Sep Sat 23, 2017 2:34 pm 
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Hi Lou,
Since my last post in July I haven’t worked on a radio. I recently bought an isolation transformer in order to be able to safely work on AA5 radios, so in the not too distant future I should have something to report. I was hoping that someone else might have tried using the generator on a transistor set, to see if my results were typical, or if I have something wrong. I know that it was designed with tube sets in mind, so what I saw is maybe what I can expect.

Enjoy the weekend,

Colin


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 Post subject: Re: Microcontroller Based Signal Generator
PostPosted: Sep Mon 09, 2019 12:32 am 
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Location: Benton City, WA
louhaskell wrote:
It has been awhile since the last post. I was wondering how everyone's project turned out and if you have found this project useful.


I am just now getting back to the project. I checked your BOM but did not see C12 listed. Yes, you told me to look at the schematic which has it and it is 100mf.

I had purchased 2 displays 2.4" TFT but when I actually took them out of the bag yesterdat I see that they have a totally different footprint than the one you used so I will have to buy a different display.

I do not have the T1-1T-X65 rf transformer and will have to look for that one since Mouser and Digikey do not have them.

I do knot know what others did for a case. 3D cases seem to be all the rage but I do not have a 3D printer and will not buy one until 3D metal printers fall into the $200 range which I suspect will be a while. ThingiVerse often has 3D case files for various projects and usually 3 outfits offer to print them for a price but will never ever give me a price before hand. They always want access to my entire account and that aint gonna happen. If they are offering to print a particular item from ThingIVers has the files then the outfit should be able to calculate cost. I do not mind doing an acrylic case but having to do it by hand means that it will not have all of the tabs and notches that yours has so if I do an acrylic case it will be straight pieces of acrylic and will use WeldOn #3 or #4 to glue all but the top together.

Thank you for the project.


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 Post subject: Re: Microcontroller Based Signal Generator
PostPosted: Jan Tue 14, 2020 6:42 am 
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Location: Benton City, WA
louhaskell wrote:
It has been awhile since the last post. I was wondering how everyone's project turned out and if you have found this project useful. Any feedback on the operation?

Lou, any idea how many of these got completed?

I had a little trouble finding the build info on your web site but finally found it at:
http://louhaskell.com/compulign/

I am actually still working on this but am expecting to complete it shortly...minus a case.

I wonder if anyone has found a ThingiVerse file for the case or if there is a piece of software that is easy to use to make a box? I have a couple of 3D programs and the one was highly tauted and free but was not obvious how to even make a simple box.

Thank you.

Jim


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 Post subject: Re: Microcontroller Based Signal Generator
PostPosted: Jan Tue 14, 2020 12:33 pm 
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Location: Dublin, Ohio
I believe there were only about 5 people who built this device. I have not heard back if they have found it useful. I use mine as both an alignment tool as well as a signal generator for both sine waves on radio and square waves for logic circuits.
The link you mentioned is a new link on my new website that is now the official home of the project.

I do not have a 3D printable case design. Like you, I have played with the software but have not had much success. There are many libraries around who have 3D printers and they will crank out a box or design for just the cost of the materials. Often they have classes in the use of the design software. Here in Columbus Ohio area, that is in Westerville Library.

Over the past couple of years I have looked at different designs for the device with the goal of reducing the cost from $100 to about $50. There are other cheap more powerful processors like Raspberry Pi and ESP32 that have more speed and advanced peripheral controls, but anything else I have designed to date still hits the $100 cost baseline. I half expect one of the Chinese companies you see on Banggood or AliExpress to offer something but no dice there as well.

Although I have greatly minimized my radio work, I would be interested if anyone has a better design that the Complign I have discussed here.

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 Post subject: Re: Microcontroller Based Signal Generator
PostPosted: Jan Tue 14, 2020 2:23 pm 
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Joined: Jan Mon 18, 2010 2:13 am
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Location: Dayton Ohio
Lou I apologize for not bringing up feedback on your CompuLign.

I have used mine on a number of occasions but so far not in sweep mode.
I need to play around with that.

Most recently on the little 3 tube radio I built.

viewtopic.php?f=12&t=310686&start=20

Ive yet to finish it, but the IF alignment went well at 455 KC.

Thank you once again!

-Steve

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Radio Interests
-Zenith
-Sparton
-Pre-War FM
Consoles and floor models, the bigger, the better!


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 Post subject: Re: Microcontroller Based Signal Generator
PostPosted: Jan Wed 15, 2020 3:50 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 2367
Location: Saskatoon
louhaskell wrote:
Over the past couple of years I have looked at different designs for the device with the goal of reducing the cost from $100 to about $50. There are other cheap more powerful processors like Raspberry Pi and ESP32 that have more speed and advanced peripheral controls, but anything else I have designed to date still hits the $100 cost baseline.


I built an AD9851 based signal generator, with roughly similar functionality, for under $20 by making use of small parts already on hand, and minimizing the quantity and price of new parts. Even purchasing all new parts, the price would likely be under $35 including power supply, but not including an enclosure. My original intention was to build just a fixed frequency signal generator with precise frequency setting (1 Hz resolution), since that was all I needed at the time. But projects tend to evolve, and I eventually added a sweep function and an audio modulation feature, since the additional parts were almost negligible.


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 Post subject: Re: Microcontroller Based Signal Generator
PostPosted: Jan Thu 16, 2020 12:20 am 
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Posts: 226
Location: Benton City, WA
BobWeaver wrote:

I built an AD9851 based signal generator, with roughly similar functionality, for under $20 by making use of small parts already on hand, and minimizing the quantity and price of new parts.

The actual AD9851 modules I am seeing are around $30 usd and am hearing that a lot of them are really mislabeled AD9850 modules. Anyway if they are actual AD9851 modules how are you using them? Do you have a drawing or schematic of your instrument?

Thank you.

Jim


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 Post subject: Re: Microcontroller Based Signal Generator
PostPosted: Jan Thu 16, 2020 6:40 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 2367
Location: Saskatoon
At the time that I bought the modules, 2-3 years ago, both AD9850 and AD9851 were selling for about the same price. A few months ago, I thought I'd buy a few more of them, but I noticed that the price of both types had shot up. The AD9850 seems to have dropped back down now, but the AD9851 is still expensive. I assume it's just due to availability of the parts.

I hadn't heard anything about mislabeling, but there were apparently some AD9851's supplied with 3.3V oscillators which could overheat if operated on 5V.

It's easy enough to tell the AD9850 and AD9851 apart, because the AD9850 comes with a 125Mhz reference oscillator, and the AD9851 comes with a 30MHz reference oscillator. The AD9851 has an internal 6x frequency multiplier, so that its working reference frequency is 180MHz, giving it about a 40% improvement in top end frequency over the AD9850. Aside from that difference, they are completely interchangeable. The module designation for both types is "HC-SR08". So, you have to read the seller's info carefully to make sure which type is being sold. The pinout is identical between the two. You only have to change one numerical constant in the program to account for the difference in reference frequency.
This is my schematic:
Attachment:
DDS_schematic_r2_2.png
DDS_schematic_r2_2.png [ 59.48 KiB | Viewed 427 times ]


In order to get the sweep rate fast enough (60 sweeps/second in 128 step mode & 30 sweeps/second in 255 step mode) I used a PIC microprocessor programmed in assembly language. This means that it requires a PICkit programmer to load in the program (unlike an Arduino that doesn't require any additional hardware). The PIC programmer is not expensive (about $12 on Ebay), but it tends to discourage a lot of prospective builders. This didn't matter to me, because I hadn't intended it as a DIY project, but a few people on another electronics forum had asked how I controlled the DDS chip. So I posted the details here:
http://electronbunker.ca/eb/DDS_Controller1.html


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