What drives the pin? What voltage? Pulse or level shift?
Some form of signal conditioning / filtering / protection needed?
What’s the interface here? Relay / contactor? Voltage and current needed?
Most embedded brds do some kind of pwr reset / boot up. I/O lines may be random until boot up is completed. Need to keep this in mind.
At first glance I’d say the your basic lowly Arduino Uno could easily do this. Not exactly industrial grade stuff. You could probably do this w/ set of 555 timers…but NO.
From what I recall of the sander - there are at least 2 - 3 DC motors w/ brushes. EMI / RFI noise may / may not be a problem.
If the ckt fails, what would be a safe fail mode?
Your spec is lacking important details that can play Gatcha
I’m not promoting a specific a design. As long as it is reliable. I just want to shut the sander down after a few seconds when a warning led is lit-up. Currently the on-board shut-down circuit isn’t functional, so we need to add one pronto. The add-on can be mounted outside of the control panel on the machine’s frame. I can even provide that part of the project if it is helpful.
Not really interested in taking the lead on this. Would like to hear from those who are more up to date on industrial grade boards , etc. My fall back go to would be the Uno because I’m familiar with it. Not sure this would be a robust reliable long term solution.
Guessing on a few things here - 1) replacement board is not available and / or ridiculously expensive, 2) users ignore the red warning lite, and 3) you want a maker proof solution.
Got a schematic for the brd that drives the red lite?
What does the shut down ckt do?
I suspect this is something that can be done with an off the shelf part, but we’d need answers to artg’s original questions. I don’t have time right now, but the right answers may mean it doesn’t require much.
The cover would be pulled and the rest is up to the developer. Does this simple solution really require a micro? We were just going to add a circuit breaker to handle this until we considered using a LED pin to drive it. The LED triggers a 555 that triggers the break in power. Doesn’t anyone remember how to use old TTL logic anymore:)
When a certain LED segment lights up, wait 5-6 seconds and if the LED segment is still lit then turn the machine off. This shouldn’t be a complex problem for a seasoned pro.
If I understand the problem correctly, an RC filter and a comparator could handle this fairly easily. Circuit would automatically reset after the warning LED goes off.
Knowing the power switch is critical to design an output stage though.
When too much is being asked of the equipment, an existing LED turns on.
If you watch that pin for high(voltage) and act on it, then that is 1/3 of the solution.
Delay for a few seconds so the user can reduce the load and make the LED go out.
If the user doesn’t take corrective action then trip a contactor, breaker, whatever to “unplug” the machine.
I would just place a breaker on it, but people want the delay.
This is not a sexy project. It is one step above a blinky app. I have other responsibilities, so I will not be personally implementing ideas tossed out. Just looking for a clever EE that can knock this out in an afternoon. This project is fully funded and ready to go.
There are a bunch of questions posed that SWA has been seemingly unwilling to address. I think the manual is here, but he’s only identified it as “drum sander:”
There’s a useful partial schematic on page 29. It’s not clear if the E-Stop signal is low level, or full motor current, but it looks like low current if not low voltage. That may make stopping it relatively easy. Probably be able to sip power from the lines that power the Display assembly.
My guess is that the load indicator is using the hall effect speed sensor to see RPM reduction as an indication of load. If you can’t easily bridge the LED drive, you may be able to monitor that.
If I were doing this, I’d try and make a reversible mod limited to insertions in between boards using existing connections. A stock machine is usually easier to troubleshoot and gt third parties to repair when needed.
Unfortunately I’ve already wasted more time that I have to spare looking for information that could have been provided. I have no time left to work on this. My boss is already complaining I spend too much time on DMS stuff and not enough time on billable work.
Dear Oz,
Yes it is our only drum sander, this is the name of a class of equipment, there is only one on the shop.
It would be less than wise to design a circuit based upon what a wood shop person suggested the parameters were. If you asked me to build a cabinet for you, it wouldn’t be smart for me to blindly go off of your measurements if your were not a professional. I would ask when I could drop by and measure things. This is why I didn’t toss parameters out there as if they were facts. This is also why I stated I wasn’t looking for drive-by help, but a full solution provider. Anyone doing this project will most likely want a blank slate. If I have to study how this crappy piece of equipment is controlled in order to answer all of your questions, I might as well develop the solution myself.
When @TBJK has made parts for this clunker he never asked me what the shaft diameter, length, or shoulder radius of the gear was. He took the measurements himself so it fits the drum sander correctly:)
Maybe this was confusing since it sounds like I have more than a passing knowledge of electronics, which I do, but I’m no EE. There are plenty of opportunities for all members to meaningfully contribute to the success of DMS.
BTW, the hall effect is most likely tied to the belt speed indicator display. The load being measured is the sum of belt speed, item weight, and friction between the drum and the board. I expect the load is derived by measuring the current required to keep the conveyor belt moving a constant rate of speed. But, hey, I’m jut one of those simple woodchucks in the wood shop:)
I look forward to you becoming more involved as your time permits.
Model number … PM2244 Stock number …1792244 Motor and electricals:
Drum motor:
Motor type … totally enclosed fan cooled, induction, capacitor start Horsepower…1-3/4 HP Phase… single Voltage…115V only Cycle… 60Hz Listed FLA (full load amps)… 14 A Motor speed … 1720 RPM Starting amps … 54 A Running amps (no load)… 6.2 A Start capacitor … 300MFD 125VAC Run capacitor …50μF 300VAC
Conveyor motor:
Motor type …totally enclosed DC Horsepower…1/30 HP Phase… single Voltage… 100V DC Listed FLA (full load amps)… 0.45 A Motor speed …40 RPM
On/off switch … magnetic, with safety key Power cord… 12AWG x 3C, 6 ft. (1830 mm) Power plug installed… 125V 15A Recommended circuit and fuse/breaker size 1 … 20A
