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Ports and Interfaces => General Discussion => Topic started by: chet on March 13, 2019, 07:42:56 am

Title: Microcomputer Reset tied to ground by capacitor
Post by: chet on March 13, 2019, 07:42:56 am

Trying to understand circuit on a Lifecycle stationary bike. Why would they tie the reset terminal on a M5L8035LP microcomputer to ground with a 1 microfarad capacitor?

Title: Re: Microcomputer Reset tied to ground by capacitor
Post by: Jan Axelson on March 13, 2019, 05:01:50 pm

This discussion might help:

https://electronics.stackexchange.com/questions/67767/connecting-the-reset-pin-of-at8051

Title: Re: Microcomputer Reset tied to ground by capacitor
Post by: chet on March 16, 2019, 07:50:05 am

In the bike application, when the bike stops all power supplies are lost except for a 9 volt battery that is used with a switch to launch voltage to the alternator field when you start pedaling.  When the pedaling  starts and the switch is pressed, the alternator develops the power for launching all power to the microcomputer.  So I guess when power is now supplied, the microcomputer may reset?  The capacitor tied to the computer reset is not tied to the power in any way. The positive side of the capacitor goes to reset terminal and the negative goes to ground.  All the peripheral chips that you mention in a setup are present including a programable chip that has the window covered.

Title: Re: Microcomputer Reset tied to ground by capacitor
Post by: Jan Axelson on March 16, 2019, 08:59:18 am

Yes, the chip might have an internal pullup.