Monday, July 12, 2010

Equipment for Everyone

This post will be about setting up your workstation at home cost effectively. This comes as a request from one of our readers. Thanks Nathan for the feedback!

Before I start, in the future this blog will be focusing more on the LaunchPad and MSP430 devices (once I get my board). Hang in there if you are waiting for MSP430 code and projects, it will come.

So… It was very hard for me when I setup my lab at home due to how little money I had. The most cost effective way to build up a lab is slowly over time as you progress in your knowledge, which is what I’ve done over the last 10 years or so. But what about if you want to go all out right away and not built up your lab over time? I'm actually in the process of updating my tools since I won't have my universities labs available to me anymore quite soon.

The following is a list of all the main tools that someone who's working with electronics would want. Some of them are quite expensive and out of the price range of most hobbyists or students. All of these will find their uses with the LaunchPad and any development board.

1. Power Supply
2. Digital Multimeter (DMM)
3. Oscilloscope (Scope)
4. Signal Generator
5. Logic Analyzer

The two most important ones which everyone should have is a Power Supply and a multimeter. One important thing to note is that good professional versions of all of these tools are out of the price range of most people. I would love to have the $5000 scope or the $500 power supply I use at work on my home bench. Not gonna happen anytime soon.


Power Supply

A power supply is important because it makes prototyping easier, I would hate if I had to worry about batteries, voltage regulator circuits and the like every time I wanted to prototype something. One nice tip I learned throughout the years is to use a computer power supply unit (PSU) as your power supply! They are very cheap and provide stable and high current power! You get 12V, 5V and 3.3V supply, what else do you really need?? If you do need other voltages I will show in a future blog an easy way to get voltages without a voltage regulator if you’re using a power supply. Just be careful if you are using one of these since they can provide a super high current, it might be beneficial for you to put in a separate fuse to protect your circuits (somewhat).

There are a ton of websites online that detail how to do this safely and whatnot, so I will not be going over this here. Here's a website I quickly found on Google. I'm going to find a way soon for comments to have pictures so anyone who has one of these up and running can post their pictures.

Look into getting a power supply if you don't have one, I could not live without mine.


Multimeter

Everyone needs a multimeter, even people who only work with digital electronics such as FPGAs. A multimeter is the most important tool you will ever own. It measures AC and DC voltages, AC and DC currents, and resistance. Newer more expensive models also do all kinds of things such as measure capacitance, inductance, and frequency.

You will need one to troubleshoot your circuit anytime something goes wrong. I'm a huge proponent of ALWAYS testing your power supply voltages before and after you hook it up to your circuit. This makes sure you do not blow your chip because of a stupid power supply mistake. Recently not using a multimeter halted my entire project since my meter broke; I decide to just trust my power supply, big mistake. For some reason my supply was wrong, and blew my MSP430 and ez430 programmer. It's not fun when that happens, trust me.

Now, about what multimeter to get; this is a tough question to answer. There are the cheap $3-$10 multimeters out there, that might suit your purposes but they are quite unreliable and prone to failure. If you have ever seen Daves EEVBlog he has quite a few episodes about cheap multimeters and the higher end multimeters. Sure, I'd like to have the Fluke multimeters (they are the best name brand), but I can't afford one. So I have mixed feelings about these cheap multimeters. I would recommend getting one if you’re a hobbyist and you realize it’s not going to be too accurate and could mess things up. Getting a wrong reading will not cost you thousands or millions of dollars as it could in a company. What am I doing to do? Well, I ordered a cheap $3 multimeter from eBay, and I'm also planning on getting one that’s in the price range of $40-60 or so that I can rely on. But to start out use your judgment. Keep in mind though that you can really get screwed with a $5 multimeter.


Oscilloscope

Oscilloscopes are in my opinion the coolest, best, and most useful tool you will ever have. I wish I had my own, but I can't rationalize spending the money on one when I can just use one at work, or go to the school labs. I won't talk much about scopes here, but I will say that Dave's EEVBlog has some interesting reviews on a really cheap ($400...who decided that was cheap?) scope from Rigol. I think it was his first blog. You can buy a PC based scope but I don't recommend it, save your money for something worthwhile (like a cool development kit).

It's possible to use your soundcard as a scope by using the microphone input. There are a few challenges with this though, the first being the voltage. You have to make sure the size of your signal will not exceed what voltage your sound card can handle. The second and major thing which turns most people away from this is the limitations in the bandwidth of the soundcard. I will not talk about this here since again, there is more than enough information on the internet about this. Google away.


Signal Generator

This is a very useful tool if you are working with analogue applications such as sensing or filtering. This is a hugely valuable tool, somewhat more so in my opinion than an oscilloscope when working on hobby projects. This is due to the fact that when you work with microcomputers you can easily get by without a scope, but if you are working with an ADC it is almost 100% necessary to have an input signal to test your code and hardware with. Aliasing can be annoying for sure; having a signal generator can help you make sure you won’t be aliasing. I will be writing a post later about using the ADCs in the MSP430s specifically, and will mention aliasing a bit.

That being said, signal generators are quit expensive so I do not have one. What do I use to test my ADC and filters when I can't make it to the labs at school or work? I use my sound card. Again, the sound card is a really cool piece of hardware which can do a lot of things! The limit of the soundcard though is that you have to work in the frequency ranges supported by your card; in most general cases that is more than enough to test an ADC or filter.

How do I generate my signal? Well, I use Matlab to do it since I do not like any of the software I have found which do this for you. In Matlab it is stupid easy to generate any arbitrary waveform (as long as you stay in the soundcards bandwidth) and play it. For those of you with Matlab, look into the command 'wavplay'.

One problem I have had with setting this up though, are weird ground loops with references on my ADC. Discussing that should be a blog in itself, so all I will say for now is be careful with your reference voltages and grounds when using the sound card as a signal generator. A cheap way to set this up is to just pull apart old headphones and solder nice connectors on the end.


Logic Analyzer

If you do a lot of work with microcomputers or FPGA's, consider buying one of these. Professional models are quite expensive but you can buy many computer based ones for quite cheap. I use Saleae's Logic which costs $150, and is well worth it in my opinion despite the few things I really don't like about it. It makes debugging chips and communication buses very very easy. I could not imagine developing for a microcomputer without it; that being said, I developed without one for years so it is not 100% necessary, it just makes life easier.


One of the first things I will do after I get the blinking light program running, is to verify that the SBW is working on the connector on the board so I can hook it up to my MSP430F2013 chip, using my logic analyzer. This can also be tested with a multimeter. One of the most useful things a multimeter has is the continuity check. I rarely use this to check diodes; I mostly use this to find which pin is connected where in complex designs with many wires. This is VERY useful for debugging and this technique should be always kept in mind.

So, this post is already quite long, longer than I would like it to be; the longer it is the less people will read it. I will be talking about getting a good set of components for development and using a breadboard and all that good stuff in a future post. I also will talk about soldering equipment and building PCBs and how I think this should be done in another post.

Comments, I love them. Help me out, what I am doing wrong? What am I doing well? Topic suggestions? Anything? I'll be keeping a list of topics and will be widdling away at them as time continues. Every now and then I might put up a pole as to which topic should be next.

Till next time.

-NJC



PS: Some unrelated World Cup humor for anyone who watched the final match.

5 comments:

  1. Cheap and good PSU:
    http://shop.tuxgraphics.org/electronic/detail_microcontroller_powersupply.html

    The Rigol DS1052E is very good and hackable into a 100MHz model.

    This is a good Logic Analyzer:
    http://www.mib-instruments.com/servlet/the-52/LA1016-16-channels-100MHz/Detail
    Remember to order probes. I bought Agilent probes really cheap.

    The software is good and still updated for this model. Unusual for Chinese companies. The software link on the website used to be wrong. Have not tested lately.

    Looking for a good signal generator. Ready or DIY guide.

    ReplyDelete
  2. @ Anonymous
    Very interesting links. The Logic Analyzer you mentioned is definitely worth doing some research on if you are in the market for a new one. But as always its important to make sure something you buy is going to be reliable. And yes, about the Rigol, I might be buying one soon depending on how much I can save up in the next few months, Dave's EEVBlog has good information on the 100MHz hack if anyone is looking for information.

    About the power supply, seems very interesting up front and caught my eye. I was a little disappointed to see that the kit did not come with a case, display, or box, but I guess is it only €24. After looking at the circuit, which was described pretty well I have some doubts. How does the output voltage look? Is it fairly noisy? What kind of stability does it have for different loads? If you have one of these and have a scope, do you think you could post a link to some pictures?

    What kind of functionality are you looking for in a Signal Generator? What kind of waveforms at what kind of frequency ranges? I might be able to recommend a few good ones depending on your price range.

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  3. For a cheap (~$40) 100MHz Logic analyzer, you want to try the OpenLogic Sniffer.

    http://dangerousprototypes.com/open-logic-sniffer/

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  4. I'm new to this so I am reading your blog from the start. My question pertains to workstation equipment. I'd like to know what you think of this portable oscilloscope for a beginner.

    http://www.seeedstudio.com/depot/preorder-dso-quad-beta-test-p-736.html?cPath=174

    ReplyDelete
  5. To be honest I never have played with one of those portable oscilloscopes, but from everything I have read they do not seem to be worth it. It would be much more beneficial for you to pick up an analog scope from eBay for the same price. Remember this is just my opinion though.

    Personally I use a Rigol oscilloscope. It's a bit more than what you mentioned but I highly recommend it! It's a great scope.

    http://www.amazon.com/gp/product/B003MYND5A?ie=UTF8&tag=msp0d-20&linkCode=as2&camp=1789&creative=390957&creativeASIN=B003MYND5A

    ReplyDelete