DiyLightAnimation
Fun => The Porch => Topic started by: chrisatpsu on April 25, 2012,
-
if i wanted to start digging into more advanced stuff i would need a scope.
what should i look for in a scope when dealing with digital circuits?
sorry if this is too techincal.
-
Depends on what you plan on looking at?
Digital stuff usually you would want a logic analyzer.
For a scope 20 MHZ, 2 channel, digital storage, probes rated for whatever voltages you plan on looking at, as a starting point.
Logic analyzer at least 8 channel.
There are several kits on the net if you are really into DIY
-
pretty much the output of dmx-pixelnet- and the chips in the nodes, pwm output. pretty much that stuff for now.
-
I have been looking at this
http://www.ebay.com/itm/ARM-Dso201-Portable-Pocket-sized-Mini-Nano-Handheld-Digital-Storage-Oscilloscope-/220976820974?pt=LH_DefaultDomain_0&hash=item33733eb2ee (http://www.ebay.com/itm/ARM-Dso201-Portable-Pocket-sized-Mini-Nano-Handheld-Digital-Storage-Oscilloscope-/220976820974?pt=LH_DefaultDomain_0&hash=item33733eb2ee)
There is also
http://www.ebay.com/itm/PC-USB-Logic-Analyzer-with-I2C-SPI-UART-decoders-and-I2C-Master-and-GPIO-PWM-/270874435772?pt=BI_Analyzers&hash=item3f115fe0bc (http://www.ebay.com/itm/PC-USB-Logic-Analyzer-with-I2C-SPI-UART-decoders-and-I2C-Master-and-GPIO-PWM-/270874435772?pt=BI_Analyzers&hash=item3f115fe0bc)
Both look ok, Havn't tryed.
I have an old tektronix scope that just collects dust.
Have Fun
-
I need a lesson to understand what a scope can do for you.
-
pretty much the output of dmx-pixelnet- and the chips in the nodes, pwm output. pretty much that stuff for now.
If that's all you need then get a logic analyzer. Even with a scope these come in handy and are designed to do specifially what you want.
-
I need a lesson to understand what a scope can do for you.
A scope lets you see the actual waveform and allows you to monitor its shape, amplitude, and frequency. This really isn't all that necessary for what Chris currently wants to do but it does help in debugging other parts of a circuit. You can see a crystal output to see if it's working and at the right frequency. You can see a digtal outpu and make sure that it exists, t form is shaped correctly and if there is enough amplitude to be detected. It can also spot unintended bias voltage on a digital signal that could prevent either the on or off states from being detected and can detect AC sign waves on a DC voltage that could be affecting other circuits. While a logic probe can see and decode a digita signal, if there is something that is not working, a scope can help determine what is wrong. The downside is that with these small SMD components, it can get real easy to short things out with the probes.
-
I have an old tektronix scope that just collects dust.
What don't you like about you're old scope?
-
I hav two of them ad it's probably just not fast enough for todays modern circuits.
-
I need a lesson to understand what a scope can do for you.
You swish it around your mouth at night and it kills germs. It helps with bad breath. >:D
-
<la.. <la.. <la..
-
Depends on what you plan on looking at?
Digital stuff usually you would want a logic analyzer.
For a scope 20 MHZ, 2 channel, digital storage, probes rated for whatever voltages you plan on looking at, as a starting point.
Logic analyzer at least 8 channel.
There are several kits on the net if you are really into DIY
The Nyquist equation says that you need to sample at twice the frequency you want to measure.
http://en.wikipedia.org/wiki/Nyquist_frequency
So if you have a 5mhz signal to measure, you need a scope that samples at 10mhz.
In the DMX512 spec
http://en.wikipedia.org/wiki/DMX512
It says 512 channels will be sent in 23ms or 44khz.
"A maximum-sized packet, which has 512 channels (slots following the start code), takes approximately 23 ms to send, corresponding to a maximum refresh rate of about 44 Hz. For higher refresh rates, packets having fewer than 512 channels can be sent." Just about any scope would work for this low frequency.
about any scope would work or DMX.
If i were getting a scope i would look to 20-30mhz sampling rate. Better quality scopes have higher sampling rates. A better scope allows you to look at the leading edge of a signal to see if it is distorted.
As an aside , i use the Nyquist equation to set the sampling rates for the automatic performance metrics that i create against database stats, os stats and network stats.
-
so how bout a Techtronic 500MHz bandwidth up to 1GS/s sample rate for about $55 would be a good find?
TDS 724A
-
so how bout a Techtronic 500MHz bandwidth up to 1GS/s sample rate for about $55 would be a good find?
TDS 724A
Yeah, it would be good. If your source falls through you can get another one here, refurbished for $6500
http://www.testequipmentconnection.com/11549/Tektronix_TDS724A.php
The scope comes with
3.5 inch DOS floppy disk drive
so you can store data too...
-
I like my Bitscope so look at them also.
RJ
-
Quote from: combustionmark on Today at 10:25 AM
I have an old tektronix scope that just collects dust.
What don't you like about you're old scope?
I like it, Just not used much any more.
4 channel, 200 Mhz, 6" screen, analog sample storage, Lots of options, 280 + Lbs, has it's own cart.
A good scope 30 years ago.
Have fun
-
LOL, I guess that OLD is a relative term. My scopes are from the 50's and they were nowhere near that fast back then.
-
if i wanted to start digging into more advanced stuff i would need a scope.
what should i look for in a scope when dealing with digital circuits?
sorry if this is too techincal.
I've been happy with my USB scope (search Ebay for DSO2090 )
More features than I know how to use. Saving screenshots as graphic files for posting has been very valuable.
some examples at: http://www.granburychristmaslights.com/DCx16.html
-
Make sure what ever you get has a logic analyser also. You do not just want a scope. I use the laogic analyser far more than the scope like maybe 10 to 1.
Some of the ones posted are just scopes and when you are working with digital circuits the logic analyser is more useful as you can look a many data lines. you can decode data streams in most ect. It cleans up digital signals to show as true square triggers so checking timing is easier ect.
RJ
-
I was just looking at the bitscope site. Wow have things changed, I may just have to pick up a new
toy tool.