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  • Author Author: jw0752
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$8.00 US Signal Generator Kit

jw0752

Every once in a while I find one of these irresistible buys from the Chinese sources. Such was the case when I came across this little Signal Generator Kit the other day from Banggood.

 

http://www.banggood.com/XR2206-Function-Signal-Generator-DIY-Kit-Sine-Triangle-Square-Output-1HZ-1MHZ-p-1060825.html

 

At the time I saw it they were having a sale of 23% off which brought the price down to $7.23. Also keep in mind that this also includes shipping from China to Wisconsin USA. I could not resist and ordered 2 of them. It took a little over two weeks for the package to arrive. I like the waiting time between when I order and when the package arrives. It reminds me of waiting for Christmas as a child. I have since learned that, many times, the waiting is actually more fun than the getting.

 

I also like the Chinese Kits as they always present a nice challenge due to the often poor instructions. It forces me to carefully analyze the kit and the parts. Most of the time they have a good screen print to the board so this becomes the primary guide along with the schematic if one is provided. This time there was both a good schematic and a well printed board. Another nice feature of this kit is that it came with a pre-cut and pre-printed plexiglass case. Here is a scan of the instructions so you can see the familiar instructions in Changlish.

 

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Once of the first things to do is inventory the parts and identify the capacitor and resistor values.

 

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Here is a closeup of the circuit board front and back:

 

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And here is the board after population:

 

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The heart and brains of the little Signal Generator is the XR2206 Signal generator chip. I was eager to see what type of quality and range I would get from the board so I finished assembly of the unit.

 

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I took some regular stick on feet and cut holes in the middle to accommodate the screws that stuck out. The screws that were sent with the kit to mount the board to the back plexiglass were too short and I found that some washers were needed to make things line up and fit properly. I also had to put some threads in the plastic (M3.5 x 0.5) for the long screws that hold the front panel in place. While the plastic was closely sized to the threads experience has taught that failure to thread usually results in breaking the plexiglass. The unit is designed to work best with a 9V to 12V power supply. I had a 9 volt battery pack handy so this is what I used.

 

Here is the unit in operation:

 

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Testing showed the actual range of the generator was from 600 milli Hz to a little better that 1.2 MHz. Square, Triangle, and Sine signal were available over the entire range. The range is selected by moving a jumper between header pins and the choice of triangle or sine waves is also selected by using a jumper between header pins. They have supplied some very nice little green header jumpers that are easily accessible from the front panel and are just about as convenient as a switch.

 

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The jumpers show a little better in this picture. The left potentiometer controls the amplitude of the sine and triangle output. It is a little counter intuitive for me as it turns the signal down in a clockwise rotation and increases it with the counter clockwise turn. Perhaps it is a Chinese convention but I will have to think about it each time I use it. The amplitude of the square wave is fixed and not adjustable. The other two controls are for Coarse and Fine frequency adjustment. They work very well and allowed me to pull up any target frequency that I tried. In order to get good looking wave forms I had to back off the amplitude to stay below the level where they clipped. I have had a lot of fun waiting for these kits and also had a good time putting them together. To top it off they work a lot better than I expected for the reasonable price.

 

John

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  • Hi John

    I read your review and it gave me a drive to shop one for myself image

    First, thanks allot for detailed review.

     

    I managed to solder my kit (see attached photos) and when I finished I connected it to a 9V/600mAH transformer.

    Acording to the intruction 9V is a legal voltage (don't know, maybe 600mHA is too much) but after 5 min of operation the 100uF capacitor just puffed with a light whistle image

    during these 5 min I connected my multipeter to try reading the frequencies with no success (I don't have a scope so this is my best solution).

     

    I wonder if you could see attached photos and manage to figure out if i did some 0-order mistake...

     

    Photos: https://goo.gl/photos/Bx41CmWwZ78eCJK86

     

    Also:

    I managed to insert it into the plexi glass... maybe they increased the screws or something...

    I i needed to break two edges on the box to make room for the power jack and to the output cables.

     

    Best regards

    Idan

  • in reply to idanre1

    Hi Idan,

     

    It looks like you did a great job of constructing the kit. The two things that seems most likely is that your power supply may have the wrong polarity or it may not be a DC power supply. The center prong of the AC adapter must receive the positive voltage. If negative voltage or AC voltage is applied to the center pin the 100 uF cap which is polarity sensitive will begin to heat up. As soon as the heat passes the boiling point of the electrolyte pressure will build up until you get an explosion or a leak of gas and fluid as it appears that you had. The current rating of your power supply will have had no relevance to the problem because at 9 volts the unit would have taken the appropriate current. If your unit was hooked up in reverse polarity for five minutes there is a real possibility that more than the capacitor got fried. You can try replacing the capacitor, making sure the power is DC and the correct polarity and try it again. There is also the remote chance that the capacitor was defective or that the polarity label was on incorrectly but this is very rare. If you don't have a scope you could also check the output with a small speaker as you should be able to hear the frequency output that is in the audio range. Let me know how it works out for you.

     

    John

  • in reply to jw0752

    Hi John

    I just want to update that I bought a new chip and replaced the old one.

    Along with the replaced capacitor, the signal generator works like a charm:-)

     

    Regards

    Idan

  • in reply to idanre1

    Hi Idan,

    Thanks for your followup to let me know that things worked out OK for you. I have found many times when I make a mistake or things don't work out right that I learn a lot more than when everything goes perfect. Keep experimenting and learning.

     

    John

  • in reply to jw0752

    Hi John.

    First off, Great review, very helpful. I've seen this signal generator on Banggood but haven't bought it yet. I'm an electrical engineering student and don't have a lot of the more expensive equipment, so I have high hopes for the very affordable kits on Banggood. I purchased an oscilloscope kit a couple weeks ago for $28, FedEx tracking says it should arrive on Monday. Do you by chance know the kit I'm talking about?  Maybe I'll post a review after I get it assembled and tested. If all goes  well I think the signal generator will be my next purchase.

     

    Thanks,

    DJ

  • in reply to tech_nut81

    Hi DJ,

     

    I just reviewed one that I bought from them for $22.

     

    https://www.element14.com/community/people/jw0752/blog/2017/04/25/building-the-dso-shell-15001k-oscilloscope

     

    I have also built and tested this one called the DSO 138 but I have not blogged about it on E-14. If this is the one you have coming perhaps you can blog about it and make a comparison good or bad to the 15001K.

     

    image

     

    John

  • in reply to jw0752

    I just read your review of the DSO-shell 15001k. That is the exact one that I have coming. Not sure why I had to pay $28 for it, I do see that it is now $22. After I get it together I'll put a comment on your review of it letting everyone get a sense of how easy or hard it is for a beginner. I've got a couple of through hole soldering builds under my belt now, so I think I can handle it. The small parts will be a nice challenge.

     

    Thanks again for the great reviews.

     

    DJ

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  • in reply to jw0752

    I just read your review of the DSO-shell 15001k. That is the exact one that I have coming. Not sure why I had to pay $28 for it, I do see that it is now $22. After I get it together I'll put a comment on your review of it letting everyone get a sense of how easy or hard it is for a beginner. I've got a couple of through hole soldering builds under my belt now, so I think I can handle it. The small parts will be a nice challenge.

     

    Thanks again for the great reviews.

     

    DJ

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