EEVblog Electronics Community Forum
Products => Test Equipment => Topic started by: luca1000 on August 31, 2013, 08:42:17 pm
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Hi,
I Like to know if exist some complete DIY (PCB and components already assembled) low cost Square generator stable from 10Hz to 500Khz with these features:
1) Variable amplitude.
2) Powered by 9 Volt battery.
3) Small size.
On ebay there are differents, but don't seem stable after 100 Khz or this is my impression.
Someone have try some of these ??
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It's called a 555 timer. They are stable to within 0.5% over operating voltage. If you use good components, temperature won't affect them much.
Now, if you need a frequency readback something like this may work better:
http://www.ebay.co.uk/itm/The-New-DDS-function-Low-frequency-test-signal-generator-module-sine-square-cis-/200950656828?pt=UK_BOI_Electrical_Test_Measurement_Equipment_ET&hash=item2ec997af3c (http://www.ebay.co.uk/itm/The-New-DDS-function-Low-frequency-test-signal-generator-module-sine-square-cis-/200950656828?pt=UK_BOI_Electrical_Test_Measurement_Equipment_ET&hash=item2ec997af3c)
You can probably use a 9V battery with DC jack clip to power it.
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This is very interested and I have already see it on ebay.
The problem is I don't see sufficient result on oscilloscope.
for example here:
http://www.ebay.it/itm/321040706273?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649 (http://www.ebay.it/itm/321040706273?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649)
I see it is not stable on 1 Mhz, but I don't know how work on 500Khz.
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I review better this:
http://www.ebay.co.uk/itm/The-New-DDS-function-Low-frequency-test-signal-generator-module-sine-square-cis-/200950656828?pt=UK_BOI_Electrical_Test_Measurement_Equipment_ET&hash=item2ec997af3c (http://www.ebay.co.uk/itm/The-New-DDS-function-Low-frequency-test-signal-generator-module-sine-square-cis-/200950656828?pt=UK_BOI_Electrical_Test_Measurement_Equipment_ET&hash=item2ec997af3c)
and seem not stable for frequency >150Khz.
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The problem is I don't see sufficient result on oscilloscope.
#1. What Scope do you have?= Brand, Model & Firmware version.
Maybe is the scope.
#2.
what you are looking is:
A) an Oscilloscope Training Kit.
http://www.gwinstek.com/en/product/productdetail.aspx?pid=3&mid=301&id=1310 (http://www.gwinstek.com/en/product/productdetail.aspx?pid=3&mid=301&id=1310)
http://www.gwinstek.com/en/product/productdetail.aspx?pid=3&mid=301&id=59 (http://www.gwinstek.com/en/product/productdetail.aspx?pid=3&mid=301&id=59)
B) or a Bench Generator.
DDS, ARB, etc...
http://www.gwinstek.com/en/product/productbcategory.aspx?pid=5 (http://www.gwinstek.com/en/product/productbcategory.aspx?pid=5)
I do not work for Instek, I just like the Brand.
#3. P.S.
To measure any Square wave, you need 20x the frequency, to measure 10 harmonics, or 10x the frequency to measure 5 harmonics,
less than 5 is not a Square wave.
#4.
Alternative, build one with Arduino or FPGA.
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The problem is I don't see sufficient result on oscilloscope.
#1. What Scope do you have?= Brand, Model & Firmware version.
Maybe is the scope.
#2.
what you are looking is:
A) an Oscilloscope Training Kit.
http://www.gwinstek.com/en/product/productdetail.aspx?pid=3&mid=301&id=1310 (http://www.gwinstek.com/en/product/productdetail.aspx?pid=3&mid=301&id=1310)
http://www.gwinstek.com/en/product/productdetail.aspx?pid=3&mid=301&id=59 (http://www.gwinstek.com/en/product/productdetail.aspx?pid=3&mid=301&id=59)
B) or a Bench Generator.
DDS, ARB, etc...
http://www.gwinstek.com/en/product/productbcategory.aspx?pid=5 (http://www.gwinstek.com/en/product/productbcategory.aspx?pid=5)
I do not work for Instek, I just like the Brand.
#3. P.S.
To measure any Square wave, you need 20x the frequency, to measure 10 harmonics, or 10x the frequency to measure 5 harmonics,
less than 5 is not a Square wave.
#4.
Alternative, build one with Arduino or FPGA.
I have the Tektronix TDS220 (100 Mhz) that I suppose is more then sufficient to show 1 Mhz square wave signal.
Now I seaching for a chaep small DIY square wave that work fine (stable) up to 500 kHz or 1 Mhz.
I serching on ebay but I don't find it
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Well I would consider this Function/Arbgen:
http://www.ebay.com/itm/AE20125-10-MHz-Sweep-DDS-Function-Generator-Kit-with-USB-and-Modulation-/261114462307 (http://www.ebay.com/itm/AE20125-10-MHz-Sweep-DDS-Function-Generator-Kit-with-USB-and-Modulation-/261114462307)
It might not meet your criteria of being battery powered, but if you buy it with a case than strap in two 9V battery in series and build up a simple regulator circuit.
It is reviewed here: Ascel AE20125 Function Generator Review and Teardown (https://www.youtube.com/watch?v=Ghypzo6YK6c#)
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Well I would consider this Function/Arbgen:
http://www.ebay.com/itm/AE20125-10-MHz-Sweep-DDS-Function-Generator-Kit-with-USB-and-Modulation-/261114462307 (http://www.ebay.com/itm/AE20125-10-MHz-Sweep-DDS-Function-Generator-Kit-with-USB-and-Modulation-/261114462307)
It might not meet your criteria of being battery powered, but if you buy it with a case than strap in two 9V battery in series and build up a simple regulator circuit.
It is reviewed here: Ascel AE20125 Function Generator Review and Teardown (https://www.youtube.com/watch?v=Ghypzo6YK6c#)
This is interested .... I like to see other review about it or opinion of someone that have purchased it ....
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Try this: http://www.mikrocontroller.net/topic/241596 (http://www.mikrocontroller.net/topic/241596)
It is in german but google translate does a pretty good job.
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Hi quarros ,
Thank you for your link.
The user that have purchased it have posted a screenshot of triangle demo and seem not good.
Hovever I like to see other test on Square and sine wave.
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Sorry that was all the information I was able to muster. Actualy I almost baught one, but than got lucky and scored a hameg and an instek F-Gen on the cheap, so Im good for now. O0
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This might be a useful project related to your question:
http://www.tele.pitt.edu/resources/lab_manuals/555Timer.pdf (http://www.tele.pitt.edu/resources/lab_manuals/555Timer.pdf)
Page 3 shows how to use Capacitance and Resistor values to tune the frequency of the timer clock. I read somewhere that it has a theoretical maximum of about 4.8 Mhz but in practice it starts to get bad anywhere higher than 1 Mhz, and it is usually best at around 300-500 khz.
Page 4-5 shows a bunch of equations to help you figure out the times, and suggestions on how to make the R1/R2 ratio help make the square more symmetrical. This looks like a nice guide to learn a little 555 timer project on. Page 5 has a problem question, it asks what values you need and what the times are for designing a 500 khz output.
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Oh, and I found a bunch of "555 Timer Frequency Calculator" resources online. Here is just one example:
http://houseofjeff.com/555-timer-oscillator-frequency-calculator/ (http://houseofjeff.com/555-timer-oscillator-frequency-calculator/)
The formulas in the previous PDF file can also be used to calculate everything:
Charge time (output high): 0.693*(R1+R2)*C
Discharge time (output low): 0.693*(R2)*C
Period: 0.693*(R1+2*R2)
Frequency: 1.44 / ((R1+2*R2)*C)
Duty cycle: Time High / Time Low: (R1+R2) / R2