search

ebastler / zmk-designguide

A short hardware-designguide for ZMK keyboards
Other
337 stars 26 forks source link

Exact value of resistor in SYSOFF section #15

Open billiororen opened 1 week ago

billiororen commented 1 week ago

image

Hi, first of all, thanks for your guidance. It was very helpful for me to design my own pcb for wireless keyboard.

In the SYSOFF section, you've specified R4's value as 100R. I'm dumb for this circuit design knowledge, so I can't tell what this value is exactly.

Does the value means just 100Ohm? Or any other value?

ebastler commented 1 week ago

Hi! I'm glad my guide helped you. The 100R is a simple gate resistor to limit gate current - not strictly needed and the value is totally not critical, as long as it does not approach the value of R7 (and forms a voltage divider that approaches 0.5 times input voltage on the output).

100R is one way of writing 100 Ohm, yes. The exact value is absolutely not critical. I'm pretty sure everything up to 20-30kOhm would work, but I only ever tested it with 100 Ohm.