Pulse Count Module - Voltage tolerance on A1 / B1 inputs

What devices are U2 and U3, I am trying to determine if the inputs are 5 Volt tolerant?
The devices are powered by 3.3 V so their inputs may not be 5 V tolerant.

According to the product page it is 5v tolerant.

@ Sprigo - The way I read that statement is the socket is 5 Volt tolerant of the host device. That’s why not knowing what device is in use leaves the door open for me.

The description of a module should never tell you about the mainboard socket specifics. That should be in the mainboard documentation and specifications of the socket itself. In this case I am comfortable saying that this module is 5v tolerant, looking at the schematics it appears the U2/U3 devices are simply 6-pin logic comparators and its unlikely they’ll be 3v3 specific parts and I am positive GHI would have said NO on the specs page if it wasn’t 5v tolerant.

@ Brett - The pulse counter module specifications say (when the ? is press) “This module can tolerate 5V signal from the Host device.” So now does this apply to the 3.3 V rail or just signals or both? Any ways in my case there is 3.3 Volts powering the LS366R, that means that a 5 volt signal on the an input would exceed the “Input Voltage” spec stated as VDD + 0.3 Volts by 1.4 volts, in other words very likely damage the LR366R device.

I am simply asking what is the U2 / U3 device type so that I may check that device’s “Input Voltage” tolerances when operating at 3.3 V.

U2 and U3 are only powered at 3v3, so they will never supply 5v input.

Do you have this module? Can you look at what is marked on top of them?

@ Brett - Yes I have two modules, but it would be several weeks to replace them if I guess wrong. The devices are tiny but I see a “TwosD” the “s” is subscripted, on them, not much help in google.

The U2 A1 input will connect to a Tacho output of a 5 V Brushless DC motor controller that is part of a centrifuge that can easily get up to 15,000 RPM. This is one part of my feed back loop to control this beast. I have learned that laboratory researchers have a tendency to run when centrifuges start making loud noises, often wondered if it that was part of their training, or read some where or work experience that they pick up that habit.

@ GHI Electronics - any chance of find out the device type for U2 and U3?


The schematic for this module is slightly out of date and a new one will be uploaded shortly. That being said, the parts in question are this part number: 74LVC1G57

The supply voltage dictates the output voltage for this part, in this module’s case, 3.3V. However, the part is indeed 5 volt tolerant and should not exceed 5.5V for the pulse inputs.

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@ Aron - Thanks Aron, this is exactly the info I required.