Just for anyone interested, I made some more tests with the proximity sensor. Here some notes:
1. cheap, those sensors are 5 bucks just and what’s left to get is a 4 channel relay bank to control the inverter (forward/stop/reverse) and perhaps a 12 Volt supply (those sensors need 6V+ but that’s often provided by inverters already)
2. stupid easy; all you need to do is measuring the delta times between sensor on/off and if it exceeds some thresholds, then you activate forward/reverse logic just as in the v4 hall sensor approach.
3. would work also for single phase but needs bigger relays
Now I’d just have to build the mount and housing for the sensor compatible to the v3 side plates. The last thing to solve : possibly a magnet holding a wheel with at least 4 inducting metal points (screws, pins,…) as seen in the picture flipping the sensor signal. The sensor it self reacts in the 4mm range so it doesn’t need calibration. This would work with extrusions and v3/v4 shredders, single or 3phase; doesn’t matter. Anyway, fun stuff; There is just a little headache how to make this as commercial unit (water, existing wiring, manuals, …).
Updates soon here again with project page and code
@deeemm, thanks i just saw it; At the end the more reliable way of measuring the running RPM is a proximity sensor and 2 magnets. I gave up on inverter feedback as it won’t apply for VFD less setups anyways. I tried the amp sensor of Mr. Kegel but I couldn’t apply this either to different setups and audiences.
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Most inverters have programmable outputs. You can use this with simple relays to create automatic reverse function. There should be the possibility to trigger an output at a defined torque or current level. You can use this to monitor if the motor has stalled.
Here is how to make it work…
Program inverter output to switch at defined torque or current level.
When activated this output activates a relayThe relay latches itself and swaps the fwd / rev control signal to the inverter which reverses the direction of the motorThe relay also also activates a second relay, the second relay is a delay-on timer relay.After a pre-defined time (eg 5 seconds) the second relay activates cancelling the latch on the first relay,The first relay de-energises allowing inverter to run forwards again.
Some caveats:
The inverter normally has several different control profiles eg how fwd / rev / run are connected. You need to choose the profile where applying a fwd signal causes inverter to run forwards and applying a rev signal causes inverter to run backwards, and removal of the signal causes it to stop. If your inverter does not have this kind of profile and requires an additional run / enable signal you will need to provide additional wiring to activate this. This may require additional an relay.
Most inverters have limited on board low voltage power supplies (24v), which means that they will most likely not create enough power to be able to drive the relays, so an external PSU may be required.
thanks all; @friedrich, i will try it out. At the end I’d like to have a complete ready-to go controller (with enclosure) for shredder and extrusion; So yes, if it can be done without a sensor but also without adjusting code (POTs are ok) then fine with me.
I used a simple ACS 712 – 20A Sensor on one of the three phases. The output is really unsmooth, however if you use the following code, all the AC-disturbance will be smoothed out.
Thats how far I got. You can easily see the zero-load consumption of the shredder and the peaks if it shreds material or thicker parts.
After that you need to program a algorithm which calculates the average over time to smooth out the current-peaks. Then you can set a limit and you are ready to go.
One more thing is that the current reading over time might change as the motor coils heat up and the resistance/current changes. This might be compensated by an additional temperature sensor at the motor. Like a db18b20 sensor.
An optical sensor might help as well to eliminate this uncertainty. I thought its easier to solve things within the electric cabinet, rather than to add mechanical sensors.
yeah, I would be interested too. Regarding stall/overtorque signal: after testing my variant against a few inverters I am now switching to an optical encoder too. I couldn’t get a clean signal out of them all, despite I’ve done my best sorting Arduino analogue-reference issues though. Makes the hole thing more generic; a one-for-all solution
@itamar, here is a picture of the encoder; be aware it needs a slightly more complicated algorithm if you use only one optical sensor. i think there ready to use boards for lathe spindle encoders which use at least 2 sensors; check the CNC forums.
@itamar, that could do too; in this case please harvest some old CPU coolers or get some from amazon (ssr cooler); those relays don’t last very long. i never tried this on a shredder motor; not sure what’s the peak amperage draw for start; usually you need a start capacitor in this case but also a run capacitor. single phase isn’t exactly a good choice for efficient high – torque applications. In case of doubt, please ask the fine folks at the [PP – Electronic – Department](mailto:hello@preciousplastic.com?subject=Eletronic Department)
hey there; sorry, with the heat wave and other things i hadn’t much time to progress on this.
@itamar : this post is currently only looking at 3phase motors using an inverter (around 100 Euro) which gives you all the inputs/outputs as parameters to dial in suited acceleration and declaration. even though; you still need relays to toggle the inverter control flows (around 20 V) for direction, stop and speed. in the case of single phase motors you have to use 220V relays which also can deal with the high currents (near 8 – 20+ Amps) which turn off/on the flow of a single phase line. as you don’t have an inverter which gives you an error signal, you have to build an encoder (old printers have quite some optical sensors; combine this by cutting out a gear like disc from plastic or carton) to detect your motor is still turning the shaft. with that you can use the same code as for a 3phase setup. i hope this helps.
Hello,It is not clear to me,
how to connect Arduino kit (5v)
To the connectors (220v)
currently used to manually turn a single-phase motor?
best regards
itamar.
@pex12, I managed to pick up a used delta inverter (VFD075M43A), I picked up a 4kw 3PH WEG motor still in its crate for the last few years, so got lucky with that.
Both of those boards have some nice extra features and definitely can take more abuse, nice find @s2019.
ok, i ordered all that stuff; @sensibill, a link to your inverter ? the solution is pretty generic as i see now; possibly i can make it work for your unit as well. i will head over to single phase. @s2019, thanks again; i went for ‘rugged’ for now but the ‘EMoRo 2560’ is darn good; evtl. this can be used controlling a auto-plunger and also metering. metering deserves an own topic; it was always tempting to build a unit which measures drawn amps per shredded kilogram but at the end this would be quite a downer to see what happens actually behind the scenes
nice, so that means the controller can go fully assembled out on the market; stand-alone with optional power supply (inverter provide this too). so what’s needed is to plug the inverter or only the motor (inverter incl.) ; neat, i love it.
