# oscilloscope and dcc



## tommyheadleycox (Oct 15, 2010)

I love DCC and trying to understand everything about it! Right now, I'd like to see for myself what the following signals "look like" on an oscilloscope and how they differ.

DCC signals coming from my central station (an Intellibox)
Pulse width modulation signals coming from various decoders and going to the motor.

And, I'd like to learn how to calculate equivalent DC voltage of the pulse width modulation signals going to the motor.

And, I'd like to measure in real time how much current is being used as I run more engines.

I could just get an rrampmeter. But then I couldn't see the shape of these cool signals.

How hard is it to learn how to use an oscilloscope to observe these things? ( do i have to take a class ?)
Can I procure an adequate used oscilloscope for this purpose for under $100?
I guess this comes under that phrase "lifelong learning" for senior citizens! Just kinda interested.

BTW, a long time ago, when I was in the broadcast tv industry, I had a basic working knowledge of an oscillosope and a vector scope in analyzing video signals.

Thanks,
Tom


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## dbodnar (Jan 2, 2008)

Tom - you can learn just about anything you need about using an oscilloscope on YouTube --- I also strongly recommend this video blog - there are a number of oscilloscope videos there, too
http://www.eevblog.com/episodes/ --- I have viewed most of his 700+ videos - great stuff
At to getting a decent scope for $100 I would not expect many such deals are available - I sold my last few scopes on Craigslist for several hundred each - the one I have now is really excellent and can be purchased for about $400 new - see:
http://www.eevblog.com/2015/01/15/eevblog-704-rigol-ds1054z-oscilloscope-features-review/ 
and
http://www.tequipment.net/Rigol/DS1054Z/Digital-Oscilloscopes/

Also, be careful of the pocket scopes - the general consensus is that they are little more than toys.

If you live anywhere near Pittsburgh I would be happy to let you use my equipment! 

dave


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## tommyheadleycox (Oct 15, 2010)

dbodnar said:


> Tom - you can learn just about anything you need about using an oscilloscope on YouTube --- I also strongly recommend this video blog - there are a number of oscilloscope videos there, too
> http://www.eevblog.com/episodes/ --- I have viewed most of his 700+ videos - great stuff
> At to getting a decent scope for $100 I would not expect many such deals are available - I sold my last few scopes on Craigslist for several hundred each - the one I have now is really excellent and can be purchased for about $400 new - see:
> http://www.eevblog.com/2015/01/15/eevblog-704-rigol-ds1054z-oscilloscope-features-review/
> ...


What a generous offer, Dave! It's a little far, at 500 + miles, but tempting nonetheless to come use your scope! I live in Chapel Hill, NC and work at UNC. I looked at the 1054z scope and even obtained a quote for the educational price! However, since this is a purely fun and tinkering venture, I'll look for something a bit lower down the food chain. What's really going to help is the url for the video blog . Thanks for sending it.

Thanks very much,
Tom


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## dbodnar (Jan 2, 2008)

The video blog is the best I have found for all-around electronics information - FYI, David Jones, the fellow who does the videos, now earns his living by doing the blog - he is really entertaining and does a very good job of explaining some very technical topics.
enjoy!

dave


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## JackM (Jul 29, 2008)

Good chance of finding a decent Oscope for $100 at a hamfest near you. A hamfest is a swap meet put on by one of the ham radio clubs in your area. Google something like "hamfest" and your state or city.

The junkier the seller's stuff, the more careful you should be. Definitely find an electrical outlet and make sure it works. You don't always find what you're looking for, but it's worth the drive.

JackM

Basic rule of any swap meet: the better the deal, the earlier it sells. Don't get there at noon.


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## JPCaputo (Jul 26, 2009)

How to use an oscilloscope has not changed since the 50s or earlier. The model you used in broadcast will do a fine job, even overkill for DCC.

I've used vintage all tube equipment to modern digital capture scopes. Tektronix keeps the basics the same. Agilent, hp, Phillips have odd controls.

Pretty much anything with 4MHz or better bandwidth is fine.

DC average voltage from a DCC signal is just the time average. 

Sometimes on craigslist or at thrift shops or vintage shops an old scope turns up. And it can be picked up for a song. A small scope ( round tube ) went for $30 a few months back


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## Dan Pierce (Jan 2, 2008)

I still have access to a tektronic 475 scope, dual trace and 10x delay time multiplier.
Great for troubleshooting if you understand the waveforms.
Important to have good probes and the ones I use are over $100 each, plus these have a 10 to 1 divider so as to not distort/load down the signals.


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## MyMiniatureWorlds (May 3, 2015)

I'm facing the same challenges as you are. I've already learnt how to measure the DCC voltage (built my own voltmeter) and how to lower it properly (OK, not so important for G scale...). And I've been thinking about purchasing an oscilloscope for some time.

The challenge for the oscilloscope - in the garden trains context - is that you want to be mobile with it. And the big oscilloscopes are not mobile, and they're expensive.

I'm seriously thinking about buying a cheap DIY DSO138 kit: http://www.jyetech.com/Products/LcdScope/e138.php. I know it's not really quality stuff, but it's very cheap and it would let me see the DCC signal.


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## JPCaputo (Jul 26, 2009)

For a cheap portable scope, check out this one. The specs look ok and price is cheap $105.

http://www.vetco.net/catalog/product_info.php?products_id=13820&gclid=CJzql97I48YCFZRgfgod_8kKOw

Now the big big question / comment is, you get what you pay for. For basic signal / no signal checking it should be fine. Ease of use? Who knows.

For portable scopes Fluke makes a great one. But they are $500+


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## Greg Elmassian (Jan 3, 2008)

Wow, that's pretty cheap. 

The frequency of DCC is about 8 KHz, so a 10 MHz scope should be sufficient to see the spikes and noise you are interested in.

Greg


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## tommyheadleycox (Oct 15, 2010)

MyMiniatureWorlds said:


> I'm facing the same challenges as you are. I've already learnt how to measure the DCC voltage (built my own voltmeter) and how to lower it properly (OK, not so important for G scale...). And I've been thinking about purchasing an oscilloscope for some time.
> 
> The challenge for the oscilloscope - in the garden trains context - is that you want to be mobile with it. And the big oscilloscopes are not mobile, and they're expensive.
> 
> I'm seriously thinking about buying a cheap DIY DSO138 kit: http://www.jyetech.com/Products/LcdScope/e138.php. I know it's not really quality stuff, but it's very cheap and it would let me see the DCC signal.


How did you go about building your own DCC volt meter? This sounds very intriguing.


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## MyMiniatureWorlds (May 3, 2015)

tommyheadleycox said:


> How did you go about building your own DCC volt meter? This sounds very intriguing.


That's very easy and cheap if some compromises are acceptable for you. I got all the info around the internet and summarized it here:
http://my-miniature-worlds.blogspot.com/2015/06/dcc-voltage-measurement.html


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## dbodnar (Jan 2, 2008)

*Scope Kit works for DCC*

Tom - FYI, I decided to give the little scope kit that was discussed in this thread a shot - found it on Amazon and (would you believe?) they delivered it today (Sunday, no less)

Took about 3 hours to put together - I had to measure a number of the components with a meter as they were not well marked and there are well over 100 individual components to solder.

Long story short it works! The photo below shows a DCC signal from a Digitrax system. 

It is by no means a full featured scope but may do what you want.

I may incorporate the scope into my modular layout so that visitors can have a better idea of what DCC is all about - we have an upcoming Maker Faire and that should fit right in.

dave


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## MyMiniatureWorlds (May 3, 2015)

dbodnar said:


> Tom - FYI, I decided to give the little scope kit that was discussed in this thread a shot...


This looks really promising. But I can see the voltage is around ~15V here. And in the G-Scale we would have 20-22V, right? Is the device able to show this kind of voltage or is the range too short?


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## dbodnar (Jan 2, 2008)

MyMiniatureWorlds said:


> This looks really promising. But I can see the voltage is around ~15V here. And in the G-Scale we would have 20-22V, right? Is the device able to show this kind of voltage or is the range too short?



The scope will accommodate higher voltages - I just had it set up with a lower voltage power supply when I did the testing. It was a unit we use for our HO modular layout.

dave


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## Greg Elmassian (Jan 3, 2008)

I just bought the same unit, as a kit. Beware of counterfeits, the manufacturers web site lists both approved vendors and people who have sold counterfeit kits.

Greg


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