GravityMon

GravityMon is the firmware most iSpindel hardware runs now: the same floating tube and tilt sensor, with a friendlier setup page and a longer list of places it can send readings. It posts over Wi-Fi with no app in the middle, and we read what it sends as it stands.

Setting it up

In Beerwright, open Settings → Fermentation devices, press Add a device, and copy the device URL.
Open the GravityMon’s configuration page, go to Push targets, and under HTTP Post paste the device URL into the URL field. Leave the format on its default; that is the iSpindel body, and we read it.
Save. GravityMon posts each time it wakes, at the interval you set, and the device list in Settings shows when it last reported.

If you would rather use its Brewfather template, that works too: it is the same body Brewfather reads, and we read that one as well. Either way, one URL, no key, no token.

SG or Plato, and why it matters

GravityMon can report gravity as specific gravity or as degrees Plato, and it says which in the body it sends. We honor that field. A GravityMon set to Plato posts something like 10.5, and we convert it to 1.042 before it reaches the chart, so you can leave the device on whichever unit you read by. Left unstated, a Plato number would look like a wildly implausible specific gravity and be charted as a gap, which is why the field is worth a sentence here.

We take the gravity the device calculates from its calibration curve, the same field every iSpindel sends. GravityMon also sends a temperature-corrected figure beside it. We leave that one alone, because your calibration and your reading of the chart live here, and a device correcting on its own terms before we see the number is a second opinion you did not ask for.

Several devices through a Gateway

A GravityMon Gateway is a small box that collects readings from several GravityMon devices over Wi-Fi or Bluetooth and forwards them, so the devices themselves can sleep longer. Point one of its HTTP targets at a single device URL and every device it carries arrives through that URL, each with its own name.

The first device the gateway reports arrives as the device you added. The moment a second name is heard, the URL becomes a bridge, and each name becomes a device of its own in Settings with its own pin. Readings from a device you have not pinned yet are kept, unassigned, until you say which beer it is in, and pinning it attaches what it already sent since that beer started fermenting. The TiltBridge page describes the same behavior in more detail, because it is the same behavior.

One thing the Gateway does not do: forward a Tilt. It can see a Tilt over Bluetooth and show it on its own screen, but it does not pass it along. For a Tilt with no phone beside it, a TiltBridge is the box you want.

Calibrate it first

Everything on the iSpindel page about calibration holds here. The gravity is the tilt angle run through the curve you gave the device, and an uncalibrated GravityMon reports a gravity that means nothing. GravityMon’s own setup page has a calibration tool that takes a handful of readings in sugar water and fits the curve for you. Do that before the first batch.

When nothing arrives

Nothing at all. The device only posts when it wakes. Check the interval, and check that it can reach your Wi-Fi from inside the fermenter; a steel fermenter in a fridge blocks most of the signal.

It posts, but the chart shows gaps at the gravity. The device is either uncalibrated or set to Plato on a firmware old enough not to say so. Calibrate it, and if it is set to Plato, either switch it to SG or update the firmware to a version that sends the unit.

Two devices, one chart. If two GravityMons post to the same URL without a gateway, we still tell them apart by name and split the URL into a bridge, exactly as with a gateway. Pin each one to its beer in Settings.

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