Products > Test Equipment
MS05000 Budget Logic Analyzer Probe Set Design
<< < (11/38) > >>
lodkolven:
Perhaps take the 5v supply from the USB-port on the MSO5000 ?

Gandalf_Sr:

--- Quote from: lodkolven on March 25, 2020, 01:54:14 pm ---Perhaps take the 5v supply from the USB-port on the MSO5000 ?

--- End quote ---
Quite a good idea.  I'll add it to suggestions for V2.
free_electron:
many level translating buffers do not like it when one of their sides is left unpowered.
last time i made a 'universal input' probe i used a simple opamp with strong output drive capability to power the input side.

essentially put an opamp like  a TS921 or TS951 ( that can drive 40 or more milliamp on its output) in unity gain. the output feeds the power rail of the level shifter
the input of the opamp is protected with tvs diodes and sent to the IO_SENSE pin of your probe.
a 1 meg resistor comes from your internal 5 volt rail to the opamp input as well.

So : if you do not attach anything to the SENSE line the level shifter gets 5 volt ( the opamp sees 5 volts through the 1 meg resistor )
if you wire the SENSE line to the power rail of the circuit under test the opamp will simply follow that rail voltage , so the level shifter gets the voltage of the circuit under test.
Gandalf_Sr:
I like the 1Meg resistor to a 5V power rail idea (except there is no 5V power rail - but I could steal one from the USB connector) idea but the datasheets for these voltage level translators (VLT) specifically say that, if either Vcca or Vccb goes below a specific voltage, they go into disabled high-impedance mode. In my latest Probe PCB revision vn1b3, the one that's being manufactured right now, there's provision for a 100k resistor from Vcca to ground to specifically disable the VLT if there's no Vcca voltage applied.

Again, good ideas for revision 2 but I guess people can easily modify vn 1b3 if they want to try that out.
Gandalf_Sr:
Here's a 3D printable Probe PCB protective back I designed today. Enjoy :D
Navigation
Message Index
Next page
Previous page
There was an error while thanking
Thanking...

Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod