Cheap Square generator stable from 10Hz to 500Khz - Page 1
Forum section: electronics / testgear

author: luca1000
author_rank: Regular Contributor
timestamp: August 31, 2013, 08:42:17 pm
content: 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 ??

author: tom66
author_rank: Super Contributor
timestamp: August 31, 2013, 09:30:05 pm
content: 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=item2ec997af3cYou can probably use a 9V battery with DC jack clip to power it.

author: luca1000
author_rank: Regular Contributor
timestamp: August 31, 2013, 10:10:18 pm
content: 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.l2649I see it is not stable on 1 Mhz, but I don't know how work on 500Khz.

author: luca1000
author_rank: Regular Contributor
timestamp: August 31, 2013, 10:14:23 pm
content: 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=item2ec997af3cand seem not stable for frequency >150Khz.

author: Unknown
author_rank: Unknown
timestamp: August 31, 2013, 11:36:04 pm
content: Quote from: luca1000 on August 31, 2013, 10:10:18 pm#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=1310http://www.gwinstek.com/en/product/productdetail.aspx?pid=3&mid=301&id=59B) or a Bench Generator.DDS, ARB, etc...http://www.gwinstek.com/en/product/productbcategory.aspx?pid=5I 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.

author: luca1000
author_rank: Regular Contributor
timestamp: September 01, 2013, 07:29:30 am
content: Quote from: JuanPC on August 31, 2013, 11:36:04 pmI 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

author: quarros
author_rank: Regular Contributor
timestamp: September 01, 2013, 10:21:11 am
content: Well I would consider this Function/Arbgen:http://www.ebay.com/itm/AE20125-10-MHz-Sweep-DDS-Function-Generator-Kit-with-USB-and-Modulation-/261114462307It 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:

author: luca1000
author_rank: Regular Contributor
timestamp: September 01, 2013, 01:08:25 pm
content: Quote from: quarros on September 01, 2013, 10:21:11 amThis is interested .... I like to see other review about it or opinion of someone that have purchased it ....

author: quarros
author_rank: Regular Contributor
timestamp: September 01, 2013, 03:01:41 pm
content: Try this:http://www.mikrocontroller.net/topic/241596It is in german but google translate does a pretty good job.

author: luca1000
author_rank: Regular Contributor
timestamp: September 01, 2013, 03:23:50 pm
content: 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.

author: quarros
author_rank: Regular Contributor
timestamp: September 01, 2013, 04:28:23 pm
content: 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

author: edy
author_rank: Super Contributor
timestamp: September 01, 2013, 04:44:20 pm
content: This might be a useful project related to your question:http://www.tele.pitt.edu/resources/lab_manuals/555Timer.pdfPage 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.

author: edy
author_rank: Super Contributor
timestamp: September 01, 2013, 04:51:17 pm
content: 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/The formulas in the previous PDF file can also be used to calculate everything:Charge time (output high): 0.693*(R1+R2)*CDischarge time (output low): 0.693*(R2)*CPeriod: 0.693*(R1+2*R2)Frequency: 1.44 / ((R1+2*R2)*C)Duty cycle: Time High / Time Low: (R1+R2) / R2