From 84432601907ee1df80f1e79551a276ec860a7b77 Mon Sep 17 00:00:00 2001 From: "Adrian A. Baumann" Date: Fri, 26 Jun 2026 08:02:33 +0000 Subject: [PATCH] Update README.md --- README.md | 15 +++++++++++++-- 1 file changed, 13 insertions(+), 2 deletions(-) diff --git a/README.md b/README.md index 1af86d4..b635988 100644 --- a/README.md +++ b/README.md @@ -41,8 +41,19 @@ Each meter has configurable **Min** / **Max** values that define its physical ra | PWM freq | 5 kHz | | PWM resolution | 10-bit | -Connect the meter coil (via a current-limiting resistor sized for full-scale) between a GPIO pin and GND. Find the correct resistor value by raising **Max Duty** slowly until the needle reaches full scale. 660 +Connect the meter coil (via a current-limiting resistor sized for full-scale) between a GPIO pin and GND. Find the correct resistor value by raising **Max Duty** slowly until the needle reaches full scale. +Here's a list of suggested current-limiting resistors: + +| Meter full-scale (I_fs) | Typical R_coil | V across coil @ FS | Series R (calc) | Nearest E12 (≤calc) | Pin current @ 100% duty | +|---|---|---|---|---|---| +| 50 µA | 1–5 kΩ | ~0.2 V | 62 kΩ | 56 kΩ | 54 µA | +| 100 µA | 0.5–2 kΩ | ~0.15 V | 31 kΩ | 27 kΩ | 114 µA | +| 200 µA | 0.5–1 kΩ | ~0.15 V | 15.7 kΩ | 15 kΩ | 203 µA | +| 500 µA | 100–500 Ω | ~0.15 V | 6.3 kΩ | 5.6 kΩ | 551 µA | +| 1 mA | 50–200 Ω | ~0.15 V | 3.15 kΩ | 2.7 kΩ | 1.14 mA | +| 5 mA | 20–80 Ω | ~0.2 V | 620 Ω | 560 Ω | 5.34 mA | +| 10 mA | 5–40 Ω | ~0.2 V | 310 Ω | 270 Ω | 11.4 mA | --- ## Building and flashing @@ -74,7 +85,7 @@ On first boot (or when stored Wi-Fi credentials are missing), the device starts After connecting, the device is reachable at: -- `http://m1730.local` (mDNS, works on most local networks) +- `http://.local` (default `http://m1730.local`) (mDNS, works on most local networks) - `http://` (shown in the serial monitor on boot) ### Factory reset (forgot password)