> On Jun 6, 2025, at 12:46 PM, gene heskett <ghesk...@shentel.net> wrote: > >> .. > I'm assuming you meant a woodworking planer? Single n. A 25" is a pretty > large machine & may use V-belts & std multi-hp induction motors. Most planers > used by us hobbyists are half that width and use cogged timing belts. Which > would be destroyed by /any/ slippage. The duplicate encoder setup sounds > good, until a prolonged run overruns one of the encoders. The only thing I > can suggest would involved a single hall device to give a once per rotation > trigger, driving a one shot, measure that period and feed it to another one > shot set to trigger if the first one slows by 5%, to drive an another much > longer period one shot showing on an LED from the second one when it fires. > It will also flash at power up until its up to speed, giving the user a > visual clue to start the feed. If it comes on in the middle of a board, tell > the user to reduce the depth of cut for the next pass. Or cut the power at > the same time. Except for the led, that is all in the arduino file. Minimal > cost. A $10 arduino could do that. Or a multicore arm64 could do it easier > but that's higher cost.
Why would a prolongeed run over load the sensors. The sensors are measuring either speed or shaft angle not accumulated rotation. One shots and triggers? Why to complex. Just compare the speeds. You don’t need a once per rotation index, you don’t care about shaft angles, only speed matters. Actualy the dual core ARM process is cheaper then Arduino. Look at the Raspberry Pi Pico. It is a dual core ARM that costs $4 and you can program in in Micro Python. The Pico can easly handle reading two quadrature encoders at the MHz speed level. Just get two $2 magnetic encoders. these are fast and have 1024 line encoders in them. Read them Using I2C about 25 times per second and when the speeds are a few percent or so apart, the belt is slipping. Don’t spend motr the $2 on the encoder, 0.1% accuracy is good enough and you can have that at the $2 price point. Somthing like this: https://www.aliexpress.us/item/3256805971765108.html?src=google&pdp_npi=4%40dis%21USD%2110.15%215.53%21%21%21%21%21%40%2112000036033485665%21ppc%21%21%21&src=google&albch=shopping&acnt=708-803-3821&isdl=y&slnk=&plac=&mtctp=&albbt=Google_7_shopping&aff_platform=google&aff_short_key=UneMJZVf&gclsrc=aw.ds&albagn=888888&ds_e_adid=&ds_e_matchtype=&ds_e_device=c&ds_e_network=x&ds_e_product_group_id=&ds_e_product_id=en3256805971765108&ds_e_product_merchant_id=5071463479&ds_e_product_country=US&ds_e_product_language=en&ds_e_product_channel=online&ds_e_product_store_id=&ds_url_v=2&albcp=20123152476&albag=&isSmbAutoCall=false&needSmbHouyi=false&gad_source=1&gad_campaignid=20127768206&gbraid=0AAAAAD6I-hGTFVe80aKnm_qXISwfO1_L7&gatewayAdapt=glo2usa Then the computer can be this: https://www.seeedstudio.com/Raspberry-Pi-Pico-2-p-5940.html?gad_source=1&gad_campaignid=12740071602&gbraid=0AAAAACiAB466mzmjSu4q9jtCxQXrJQljL Raspberry Pi Pico 2 seeedstudio.com Poswe can come in via the USB port from a phone charger or maybe there is already 5 volts available some place else. Magnetic encoders are very easy to use. If the shaft is steel the magnet can stick to the shaft end and then the encoder mounts to a peice of plastic or aluminum and has about a 1mm air gap from the magnet. There is room for some imprecision, getting within 2 mm is “good enough”. The magnet need not be exactly concentric with the chip-sensor. You can super glue the magnet if you like. All the software has to do it raise a pin to high if the speed ratio is wrong. It can check a few dozen times per second and wait untill it has been wrong for maybe a 10 times in a row and still shut the motor down a half second after it starts to slip. _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
