# How to add input LED to Kassutronics ASR

**URL:** <https://lookmumnocomputer.discourse.group/t/how-to-add-input-led-to-kassutronics-asr/1296>\
**Category:** DIY STUFF\
**Created:** [June 23, 2020, 9:08pm UTC](https://lookmumnocomputer.discourse.group/t/how-to-add-input-led-to-kassutronics-asr/1296 "2020-06-23T21:08:09Z")\
**Posts on this page:** 1\
**Showing post:** 17

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**Author:** ![fredrik](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/fredrik/32/682_2.png) [@fredrik](https://lookmumnocomputer.discourse.group/u/fredrik)\
**Post date:** [June 27, 2020, 10:52am UTC](https://lookmumnocomputer.discourse.group/t/how-to-add-input-led-to-kassutronics-asr/1296/17 "2020-06-27T10:52:00Z")

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> [@Pedal-O-Matic foot pedal module](https://lookmumnocomputer.discourse.group/t/pedal-o-matic-foot-pedal-module/1210/1):
>
> I added the two extra opamps

If you’re only looking for zero crossings, you can just feed the signal to one opamp’s + input and tie − to ground, and the output will swing to max when the signal crosses zero (if the input can be outside the safe common mode range, add a voltage divider on the way in). Doesn’t give you the same trimmability, though.

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