This single channel scope kit could be useful for low frequency work
www.youtube.com/watch?v=L-lwDoEee2I&NR=1
Sparkfun supply a kit for $45.95.
www.youtube.com/watch?v=L-lwDoEee2I&NR=1
Sparkfun supply a kit for $45.95.
Low cost scope
- Thread starter MFB
- Start date
That kit has been around for a while. And the prize is amazing.
Problem is, it has only a single channel, so you can't look at a signal in relation to another (e.g. clock vs. data) or trigger on a signal different from the one you are looking at.
Voltage range is very limited - can't look at very small or very large signals. And 64 pixels vertical means a usable resolution of just 6 bits for a full-scale signal (doesn't help that acquisition is 8 bits, since you can't see anything that fine). Shows that a signal is present, but not much more.
Setting up the thing through a few push buttons is a pain as well once you try to do serious work (as opposed to just getting a demo trace on the screen). Way to many key presses to e.g. change the trigger level.
With all of the above I consider it a toy (a nice one though), not an instrument suitable for real work.
Problem is, it has only a single channel, so you can't look at a signal in relation to another (e.g. clock vs. data) or trigger on a signal different from the one you are looking at.
Voltage range is very limited - can't look at very small or very large signals. And 64 pixels vertical means a usable resolution of just 6 bits for a full-scale signal (doesn't help that acquisition is 8 bits, since you can't see anything that fine). Shows that a signal is present, but not much more.
Setting up the thing through a few push buttons is a pain as well once you try to do serious work (as opposed to just getting a demo trace on the screen). Way to many key presses to e.g. change the trigger level.
With all of the above I consider it a toy (a nice one though), not an instrument suitable for real work.
Very nifty, & it's 1MHz analog. bandwidth looks a decent step up from mostly free sound card based offerings. However you'd really need a decent hands on with it to form a decent opinion, as the ergonomics look a tad unfamiliar. It'd be fun building the kit, & the price should appeal to skinflint educators! Stan.
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I'm sure it's a fun toy and nice as a demo display. I'm sure it can provide useful data for lower frequency stuff. And it is great value for money.
But putting aside fancy demos , you should asses a device on whether it can do the job and NOT whether it looks pretty on UTUBE. Or is it your design MFB and you're plugging it ?
Many of us PIC programmers have done a 'scope as the next project on from flashing an LED. I did one with rotary knobs so it even looked like a 'scope.
Many of the limitations have been highlighted by Womai who has designed a nice one himself.
But a 'scope needs serious front-end electronics to make it a useful tool.
It's not until you design one that you see the required sophistication to make a device that is really useful.
There's too much to go into here, but there's more to it than just sampling rate.
But feel free to buy one and let us know how you get on.
Anyway, I'm being too picky - great price.
But wasted if it doesn't do the job you want it for - and it won't impress girls.
If you want to save money and are prepared to build then look at the kit on offer.
If you want to spend a little more then there are a plethora of cheap low-spec flashy looking scopes about. Whether Velleman, PICOscope or a.n.other 'Tek-lookalike' brands.
Is that 1MHz sampling or the ability to show a 1MHz sine wave? Or 1MHz square wave?
Any anti-aliasing?
I'm sure you will have a dozen postings showing "My Favourite Cheapo".
Bottom line: you get what you pay for. (we've been here before several times...)
But putting aside fancy demos , you should asses a device on whether it can do the job and NOT whether it looks pretty on UTUBE. Or is it your design MFB and you're plugging it ?
Many of us PIC programmers have done a 'scope as the next project on from flashing an LED. I did one with rotary knobs so it even looked like a 'scope.
Many of the limitations have been highlighted by Womai who has designed a nice one himself.
But a 'scope needs serious front-end electronics to make it a useful tool.
It's not until you design one that you see the required sophistication to make a device that is really useful.
There's too much to go into here, but there's more to it than just sampling rate.
But feel free to buy one and let us know how you get on.
Anyway, I'm being too picky - great price.
But wasted if it doesn't do the job you want it for - and it won't impress girls.
If you want to save money and are prepared to build then look at the kit on offer.
If you want to spend a little more then there are a plethora of cheap low-spec flashy looking scopes about. Whether Velleman, PICOscope or a.n.other 'Tek-lookalike' brands.
Is that 1MHz sampling or the ability to show a 1MHz sine wave? Or 1MHz square wave?
Any anti-aliasing?
I'm sure you will have a dozen postings showing "My Favourite Cheapo".
Bottom line: you get what you pay for. (we've been here before several times...)
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westaust55
Moderator
Womai is being modest here.
His own PICAXE 28X1/2 based 2 channel project is well worth consideration:
http://www.rev-ed.co.uk/docs/KIT120.pdf
http://81.134.141.187/epages/Store.storefront/?ObjectPath=/Shops/Store.TechSupplies/Products/KIT120
His own PICAXE 28X1/2 based 2 channel project is well worth consideration:
http://www.rev-ed.co.uk/docs/KIT120.pdf
http://81.134.141.187/epages/Store.storefront/?ObjectPath=/Shops/Store.TechSupplies/Products/KIT120
premelec
Senior Member
Multi channel digitial info
Note that with a little cleverness a single channel scope can show more than only one signal timing condition - particularly with digital signals... just add the signals with different gains - resistive dividers will do... then the signal observed will have steps in it in accord with the imposed other signals... works in a pinch if all you've got is one channel to work with and you need to know more... and if you've got 2 channels you can turn that iinto 4 channels of info etc... with analog signals it gets pretty strange...
Note that with a little cleverness a single channel scope can show more than only one signal timing condition - particularly with digital signals... just add the signals with different gains - resistive dividers will do... then the signal observed will have steps in it in accord with the imposed other signals... works in a pinch if all you've got is one channel to work with and you need to know more... and if you've got 2 channels you can turn that iinto 4 channels of info etc... with analog signals it gets pretty strange...
From the long distant past: scope switches - oriiginally done with tubes (valves), then discrete transistors, then ICs. OK for low frequency/speed signals but the chopping creates aliasing at higher frequencies/speeds.Note that with a little cleverness a single channel scope can show more than only one signal timing condition - particularly with digital signals... just add the signals with different gains - resistive dividers will do... then the signal observed will have steps in it in accord with the imposed other signals... works in a pinch if all you've got is one channel to work with and you need to know more... and if you've got 2 channels you can turn that iinto 4 channels of info etc... with analog signals it gets pretty strange...
Not sure if I still have one in the back of a cabinet or not ;-)
John
BeanieBots
Moderator
But premelec's tip neither chops nor alternates. It superimposes.
A little tricky to interpret unless the signals are nice shapes but a nice trick none the less.
I've even resorted to a humble LED waived furiously by hand to determine a rough estimate of PWM duty in the past!
A little tricky to interpret unless the signals are nice shapes but a nice trick none the less.
I've even resorted to a humble LED waived furiously by hand to determine a rough estimate of PWM duty in the past!
In case somebody is interested, I am about to release a new design (early next year), based on a dsPIC. Similar to the Picaxe scope (e.g. it has two independent channels), but
- 10x the sample rate (10 MS/sec),
- 3x the bandwidth (1 MHz),
- 5x the acquisition speed,
- it has pretrigger capability (so you can look at what happened before the trigger event, which often is what you want) as well as loooong post-trigger delay (e.g. for scanning through a long data pattern).
Communication and power supply though USB. At the same time much smaller (about the size of a computer mouse), less than half the component count, still entirely made of DIP and through-hole components (thus easy to put together even for a beginner), and accepts standard 1:1 and 1:10 scope probes.
Like the Picaxe scope it is driven from the PC (allows for much more elegant, responsive GUI and cuts down on component cost; I added a datalogger mode (roll mode) for slow timebases, and infinite persistence mode, which both were a common requests for the Picaxe scope).
In other words, I really made an effort to make it usable under real-world conditions and attract pretty girls (but Dippy says a scope never does that? shoot!
Other than that, if you want to spent a lot more money (for admittedly more power), here are my current favorites (I did a lot of competitive research before I started this new design
Velleman PCSGU250 - USB scope and signal generator in one box, decent specs in terms of bandwidth, sample rate, other capability. The Software GUI is quite usable (I own the "big brothers", i.e. PCSU1000 scope and PCGU1000 generator, which use almost the same software). Costs around US$250 which is a pretty good deal, much better than many competitors.
My new favorite though - Rigol DS1102E; that's a standalone 100 MHz scope, very deep memory (1 MB), great build quality (just look at pictures of the inner design - the PCB layout is a beauty, and everything is well shielded; actually Rigol makes some of the low-end scopes for Agilent, who simply rebrand them and sell them, for 2-3x the price), and very professional handling (equal to the Tektronix and Agilent scopes I use at work that cost 20 - 200 times as much). The lower end version (DS1052E, 50 MHz bandwidth, everything else is the same) can be found for under US$400. The DS1102E has quickly become my workhorse for all microcontroller related things.
Wolfgang
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