24V keypad


I have a keypad from Storm Interface which mentions in the datasheet that it is having an Operating Voltage of 24V DC maximum. It is that maximum that confuses me. I am using a MKR1000 board which operates at 3.3V. Does this mean that the keypad might work on 3.3V voltage? Is there a disadvantage on working at a lower voltage?

Thank you

If it is a passive matrix, there should be no problem operating at 3.3V.

The value you quote is a maximum voltage

Thank you for the prompt reply. The only information I have is the datasheet. I expect it to be passive based on the sentence on the first page "Simple row and column circuit matrix, terminated by a male square pin." Also the operating current of the MKR1000 is 7 mA per pin which is well below the maximum 50 mA of the keypad. So I would expect it to work, but wanted to be sure.

The typical current in a button is 0.1-1 mA, depending on the value of your pull-up resistors and supply voltage.

Again, this are limits, for both the pins and the keypad. Just don't exceed those values. When using the internal pull-ups, which I suppose are somewhere in the tune of 20kΩ, you'd have about 165 µA flowing through the pins.

It looks like a standard key matrix, the keypad library will be able to read this thing.

It is entirely clear from the datasheet that this is simply a particularly robust and vandal-resistant matrix keypad with row and column connections. You can use it with a keypad library or your own code. The contacts are specified as "Gold on nickel plated" which means that they are suited to logic circuitry with negligible "wetting" current and not switching any significant power with a 50 mA absolute limit. The 24 V limit relates to the possibility of arcing at higher voltages which would damage the contacts.

Clearly these are limits to be avoided by a wide margin, like the 40 mA limit on a ("classic"; lower on the MKR) Arduino pin and not by any means an indication of operating conditions.