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.
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...
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), butWomai 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