Entry Level Starter Kit Including "Function Generator" and "Scope" (under $20?) - Page 1
Forum section: electronics / beginners

author: Electro Fan
author_rank: Super Contributor
timestamp: December 15, 2014, 02:13:11 am
content: Ok, lots of discussions on the EEVblog about "what is the right entry oscilloscope?" Also, even before getting a scope "what is a good way to get started with $100 to $200 in other test equipment and parts?" After trying to figure these things out with a lot of trials and plenty of errors (plus a ton of help from this OUTSTANDING forum – Thanks Dave and all EEVers) I started to make some suggested lists.I'll post the lists but first I thought I'd take however much heat this post is going to bring.In making the lists it became apparent that it’s hard to get everything you want for $100, $200, or even $500; any list requires some tradeoffs depending on your budget and what you are trying to do (build, fix, learn, etc.) - but over the last couple weeks I stumbled on to some things that gave me an idea for a "$20 list".*---* There is a bit of a "Catch-22" in the list. The more you know about electricity the more you can get the price of a starter kit down; so even though you can prove some things with the $20 list, you might not be able to do or learn enough with the items on the $20 list to make these items really useful, and you might have been able to do more or learn faster and better if you had started with the $100-$200 list. IMO, in case you aren't already highly familiar with it, a starter kit should be selected to get you well acquainted with Ohm's Law, if not more.---With all that said, I found that as shown in the breadboard photo I could make a very rudimentary “function generator” with a 555 chip. There are lots of diagrams and tutorials on the web for 555-based circuits and I’d encourage anyone who hasn’t played with a 555 to study the chip and the possibilities. I modified one 555-based circuit by substituting the recommended resistors with two potentiometers (you might try 10k POTs). With the two potentiometers I found I could easily change the amplitude, frequency (from about 1kHz to 10KHz), and duty cycle. I also found that in squaring up the square wave (by adjusting the two POTs) I could get waveforms that reminded me of the probe calibration process on an oscilloscope. The 555 circuit was powered by an entry level (Korad KA3005P) power supply.Next I came across “Winscope” – software that can be downloaded from the web:http://www.zen22142.zen.co.uk/Prac/winscope.htmWhile Winscope is very primitive compared to an entry level analog or digital scope it does display some waveforms (see images from probing the speaker terminals). Clearly, Winscope isn’t Rigol (or Agilent, or Tektronix, etc.) – but it was free.It dawned on me that the price for generating controllable waveforms and observing them was getting pretty inexpensive. So, the last step was to take the DC Power Supply out of the circuit and replace it with a simple 9V battery – and voila – an “oscilloscope” and a “function generator” for less than $20.$20 or so assumes you need to purchase a breadboard, some wires, maybe alligator clips, the 555 chip, and a few other items - and it assumes that you have a PC with a soundcard to host Winscope. (I also included an outboard speaker to hear the frequency adjustments made with the POTs but you could probably feed the audio signal back into the sound card and hear the results on your PC speakers although I’m not sure if the jack part would cost much less than a small external speaker.)Would this keep anyone highly satisfied for a long time? Maybe/probably not. Would you want to add some other things (like a ~$15 or better DMM), etc.? Sure. It all depends on your budget, how early you are in the learning process, and how hungry you are to learn – but I think it’s possible to get started for $20. For $20 there is a way to get some hands-on experience with something resembling circuit-making including the ability to generate/control and observe (see and hear) changes in signals. With an entry DMM you could more easily measure the results, and still be under $40.I'm giving some more thought to the starter lists but I'm pretty sure that a couple recommended items beyond the $20 starter list would include a DMM and a DC Power Supply. I think the ability to flexibly set voltage and max current (and see the voltage and current draw) with the Power Supply plus the ability to use a DMM to make selected voltage, current, resistance and other measurements makes these 2 tools too valuable to leave out of the kit. So while it's possible to do something for $20 I'd put a DMM and a DC Power Supply plus a nice wire cutter and some extra 22 gauge solid wire and various parts (including a few LEDs, resistors, and other parts either new or scavenged from dead electronics) on the list. These items will probably drive the price above $100 and maybe close to $200 - but you would be solidly on the path. Then find your first scope and you are on a tremendous journey.EFPS, I am definitely not advocating Winscope vs. an old analog scope or a digital scope – I’m just saying there is a way to get some hands-on experience with something resembling circuit making including the ability to generate/control and monitor signals - for $20 or less. As mentioned, I think a DMM and a DC Power Supply should be high on the list of tools to acquire - and then it might be time for an oscilloscope.

author: pickle9000
author_rank: Super Contributor
timestamp: December 15, 2014, 02:56:55 am
content: If all you have it 20 bucks I say have at it.