Built an arduino-based monitor for water flow and temp using a DS18B20 digital temp sensor and Hall Effect flow sensor. LCD shield that I had laying around sits on top of an Uno in a 3d printed case stuck to the top of the electronics-side lid. Arduino output controls a relay module that interrupts the P pin on the laser power supply (in series with the lid switch). If the water temp gets to high or the flow too low, the laser is disabled.
Works great when I’m cutting (using K40whisperer). But when I run it for vector or raster engraving, the display reads ~127.00C for temp (this is what the code returns if it can’t get a response from the sensor) and the flow reads high and jumps around.
I thought it might be a noise issue with the power supply and already meant to add an outside PS for the non-laser components so I got a Meanwell triple-output (5/12/24VDC) PS and set that up but the monitor still flakes when I’m engraving.
Seems like I either still have a power noise problem due to the shared ground/common between the new PS and the rest of the thing, or I need to move my sensors. They’re currently in the laser compartment, with the flow sensor literally lying against the tube, and the temp sensor taped to the output hose right at the tube’s flange. But it seems preferable to keep them where they are: keeping the temp sensor right at the output and the flow sensor right at the input tells me the real temp of the tube and immediately if flow to the tube is interrupted.
Anybody else had to deal with noise from the power supply? Any guidance?
Most of the time these kinds of problems are caused by poor grounding design.
Also if there are any corona or arching (no matter how small) controllers will go wild.
Here is a post I did on this some time ago. I use these rules and techniques and have not had noise problems in my K40 or my CNC.
Pay attention to ground loops. They usually are from daisy-chained power sources.
The wire length can matter in high current and static environments.
Having digital electronics near the tube is a challenge due to the static charge on the tube…
You can try some cap filters on the DS18B20’s power rail.
You could re-evaluate your sensor location…
Are you really getting an accurate reading taped to the tube (plastic or silicone) as that is not a very good thermal conductor? I would imagine that the sensor could be anywhere in the output circuit of the tube. An overtemp should shut down the LPS.
I would expect that if the flow to the tube stopped you could put the flow sensor anywhere in the tube’s input circuit and be ok. The flow sensor should be set up to shut down the LPS and that is plenty fast as the temp will not rise instantaneously.
Both my sensors are at the tank far away from 20,000V.
Very nice! For the arduino code, I would put a piezo buzzer on it and give a warning at a temp just prior(23C) to shutoff( 25C? ) so that you are warned and might be able to pause the job, add some ice and then continue.
For locations of things, I’m with Don on putting the stuff downstream of the tube. My flow display(wheel) and temp sensor is outside the machine on a shelf just above the machine and inline in the hose before it dumps back onto the reservoir. I also like having the flow meter after the tube so any damage/break in the but will give me immediate indiation and I don’t pump all the reservoir water into the machine and onto the floor before I know something is wrong.
Should have mentioned the arduino also has a red/green LED and a piezo tone. Putting together an instructable is on my list, if I get to that I’ll link it here.
Yeah, I wasn’t really impressed with just using packing tape to put the temp sensor on the silicone hose but that’s what OMTech shipped it with for their cheapo LCD thermometer. Didn’t want to deal with putting the probe in a fitting and worrying about flow restriction and/or one more set of possible leaks. When all this is dialed down I’ll goober it up with temp grease inside some kind of sleeve.
Just tried moving the temp sensor outside the case and that noise did go away during a raster engrave. Soldering up some extension cords for the sensors (at least I did think to put connectors on those leads in the first round) and will move both sensors.
OK, I think I’m good even if the sensors aren’t where I’d prefer. The flow sensor is on the hose just above the reservoir (5G bucket) under the bench and after wrapping it with self-fusing silicone tape from the metal to the wire the temp sensor is actually in the bucket, at the top of the water. Now I can engrave and the monitor’s readings are stable.
(Amazon reviews of that temp sensor noted that it’s not actually waterproof so I sealed it from the metal to the wire but the metal is still exposed)
I heard too many stories about broken tubes and damaged tubes from flow issues and temp issues so one of my first add-on items was something like this 3-way visual flow indicator. https://www.aliexpress.us/item/2255800952363993.html
2 open ports are used for INPUT/OUTPUT fittings and the 3rd is where the temp sensor goes.
Your Arduino setup adds the extra benefit of audio warnings and auto shutoff. Please do share your Instructable when you post it.
