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Low cost logic analyzer probe for Rigol MSO5000 EasyEDA project

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tv84:
Show us some pics.  :)

S. Petrukhin:
 :)

S. Petrukhin:
I recommend replacing R17.
I used 100 Om, but the led was very bright, replace to 5.1 kOm.

Gandalf_Sr:
Looks good.  The 5.1k LED resistor should allow for 3 or 4 mA of LED current which is good.  Looking at the datasheet for the SN65LVDS1, it says that the Absolute Max Vin is Vcc+2 volts so, with Vcc at 3.3V, you should be OK for 3.3 or 5V logic signals.

I see you have tantalum capacitors on the LDO regulator - I'm not a fan of Tantalums because a) they are expensive and b) they can fail explosively!  Make sure you pick a voltage rating that is at  least twice what you will be operating them at.  If you can replace them with MLCC capacitors, I would make that change - more reliable and cheaper.  There are some aluminum polymer capacitors that can replace tantalums but they are only available for low voltages.

S. Petrukhin:

--- Quote from: Gandalf_Sr on August 31, 2020, 11:12:38 am ---Looks good.  The 5.1k LED resistor should allow for 3 or 4 mA of LED current which is good.  Looking at the datasheet for the SN65LVDS1, it says that the Absolute Max Vin is Vcc+2 volts so, with Vcc at 3.3V, you should be OK for 3.3 or 5V logic signals.

I see you have tantalum capacitors on the LDO regulator - I'm not a fan of Tantalums because a) they are expensive and b) they can fail explosively!  Make sure you pick a voltage rating that is at  least twice what you will be operating them at.  If you can replace them with MLCC capacitors, I would make that change - more reliable and cheaper.  There are some aluminum polymer capacitors that can replace tantalums but they are only available for low voltages.

--- End quote ---

Yes, SN65LVDS1 have tolerant input for 5V. In addition, the logic of 5V TTL never have a logic level" 1 " equal to Vcc, it is always a little less, because this logic is based on bipolar transistors that have a voltage drop at the junction. The ringing of the signal on the fronts is successfully suppressed and dissipated on the input resistors.

I use a lot of tantalum capacitors, ever had a problem. Soviet space and military equipment was saturated with these capacitors. In my opinion, they are good. Here I used only 2 very inexpensive capacitors. I think you needn't be afraid of them. However, the project is open, you can clone it and change the board to any capacitors you like. You can make changes as you wish without restrictions.

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