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David Patel

davidp11

@david-patel · Joined March 2025

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Facility manager · hospitality · new to IoT

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Viewing 15 posts – 46 through 60 (of 62 total)
Posted · in Cheap way to drive a 700 mA LED that I dim from a board slider #5

I did a lot of lighting retrofits at the hotels before I touched any IoT, so this one I know.

Get a constant current buck module with a dim input. The cheap ones built around a PT4115 cost a couple of dollars, come in 700 mA versions (or set by a sense resistor), take 12 to 24 V and have a DIM pin. A Mean Well LDD-700H is the nicer branded one. Feed it 12 V, LED on the output, and your ESP8266 PWM pin straight into DIM. 3.3 V PWM is enough for both of those. Around 1 kHz PWM, no flicker you can see, the driver keeps the current flat as the LED heats up.

On the Hermetry side: add a command like light.set with a number parameter to the profile’s catalog as a Basic command, then a Slider control card that runs it. The slider sends once when you let go, not while dragging. For a light I switch off Ask before running, otherwise the shift lead gets a confirm box every time. Bind the current value to what the ESP reports back (I send light.level after each change), so the slider shows what the light is really doing. Control cards walks through it.

Accepted solution♥ 7
Posted · in pH alarm for a hydroponic tank that swings every time the dosing pump runs #3

I’m still learning this stuff, but I set up the same kind of alarm for the pool chemistry at our hotel, so I can do the second half.

There’s no “between” in alarm conditions, you write it as a group. The form does one comparison per severity, so switch the rule to JSON mode:

"severities": [
{ "severity": "MAJOR",
"condition": { "any": [
{ "key": "ph", "op": "<", "value": 5.5 },
{ "key": "ph", "op": ">", "value": 6.5 } ] } }
],
"debounce": { "mode": "duration", "raise": 300, "clear": 60 },
"hysteresis": 0.1

The duration debounce is what stops the dosing dip. The condition has to be true for 300 seconds by the device’s own timestamps before the alarm opens. Our chlorine dose dip lasts about two minutes, so 5 minutes was safe. Since you report every 30 s that’s ten readings in a row, plenty.

Hysteresis 0.1 means it clears at 5.6 or above on the low side, 6.4 or below on the high side, so it doesn’t flap at the edge.

All of this is on Alarm conditions reference, and the debounce part on the page next to it.

Accepted solution♥ 4
Posted · in Request: work out a robot’s zone from signal strength of BLE tags inside Hermetry #6

Running on 2 robots since last week. The 6 dB rule was necessary, without it the zone flickered every few seconds in the lift lobby. The kitchen alarm fired once already, a cleaner took a wrong turn after a map update on the robot, and housekeeping caught it in a minute. Still would like the request though, doing it in every robot’s firmware is work.

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Posted · in Our IT guy wants something we can host and take with us. Where does Hermetry keep our data? #5

Tyler this is perfect. Showed him the Residency page (we’re US, no residency requirement set) and he calmed down a lot once he saw the export plus history API route. He wants your monthly CSV idea as a standing job, so I guess that’s my next project. Not mentioning the docker thing again, lol.

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Viewing 15 posts – 46 through 60 (of 62 total)