FAQ/Banding from ground loops and shared power
This one comes from your rig, not your scope — specifically electrical noise coupling in through shared power or an external trigger. The signature that identifies it: banding that moves up the sensor, present at low to moderate LED values around 16–24 rather than only when the LED is high; sensitive to LED power and sometimes to the EWL, but not to gain. That gain-independence is what separates it from FAQ/Horizontal stripes from the EWL driver, which is worst at maximum gain. In the reported case only one person in a lab of several scopes was affected — the only one using an external trigger. Causes identified: a 3.3 V trigger line from a Raspberry Pi running on its own switching power supply; and USB LED lighting sharing a USB bus with the DAQs, or simply running too close to them. The fix that worked outright: power the Miniscope from the DAQ's power jack instead of over USB. This means opening the DAQ case and moving a jumper, and it resolved the problem completely. Supporting mitigations: put USB lighting on its own supply, and plug the switching supply into the same power strip as the computer so everything shares a true ground.
More help on this wiki
- Data Acquisition Box — The power jumper and DC jack that this fix relies on.
- Guide/How to test and debug your Miniscope V4 — Isolating rig noise from scope faults.
- Coax cable characterization — Cable and supply interactions that make noise worse.
Still stuck? Bring it to the drop-in office hours, browse the full FAQ library, or see Guide/Common pitfalls and FAQs.
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Original Google Group threads
These are threads on the external Miniscope Google Group, not pages on this wiki. They are where this answer came from and are kept for attribution and context. For anything new, please use the wiki forum above instead.
| Google Group thread | Activity | Answered by |
|---|---|---|
| scanlines caused by 3.3v trigger | 2023-01-20 → 2023-01-23 | David Protter, Federico Sangiuliano |