Question about MAX3232RTC and Fairchild QRB1134

On the MAX3232 the datasheet shows a resistor between Vcc and INT/SQW (Leg 5) but they don't show the value I would appreciate any suggestions/recommendations.
Also if anybody has used the Fairchild QRB1134, I would like to hear any comments. I plan to use in an RC airplane to meassure the RPM while in flight.
Thanks in avance for any help


Senior Member
The resistor is the open drain pullup resistor. Its value isn't critical. Something like 4.7k to 10k should work well.

I haven't used the reflective sensor, but from the data sheet, its application should be straightforward. The mounting distance from the reflective surface seems to be important, though. In the data sheet, it's specified at 0.150 inch. In the description, it's listed as within 0.200 inch. So I guess you need to figure out how to mount it close to your prop.

Good luck!