How-to using the above sensor (and some discrete components in lieu of ADC board).
This seems like the long way around. Why not just power off the motor circuit?
Lots of reasons:
- A clamp requires no changes to the equipment. It sniffs the current from the power cord.
- No high-voltage circuitry.
- Doesnât void warranties
- Easily removable/reversible.
- Approach can be replicated across multiple machines without changes.
- Can be moved to new equipment if replaced.
Most of your arguments reasonably apply to both approaches or donât apply in the DMS case.
Absolutely true, but where in the woodshop has this been a significant concern?
FWIW, the RFID Interlocks do exactly this kind of clamp on current sensing, and it works fine. But there are different considerations driving that decision.
Absolutely accurate and largely inapplicable. The vast majority of our machines are well out of warranty and internally maintained.
Besides, much of making is about voiding warranties 
All true, but also true of direct connection to the motor circuit if done correctly. So no net advantage.
I believe simplicity has value. More parts, more things to break. Finding a tap point for motor power on these machines is not rocket science. Making that connection invisibly reversible is likewise generally not difficult. The advantages you attribute might apply in highly integrated small consumer devices with molded, sealed circuits, but not on woodshop (or other most other shops) equipment.
If you gotta use current sensing, why not use one of the adjustable sensing switches? The DMS designed interlock uses these:
The current threshold is adjustable from under an amp to 150 Amps. Most of our machines are well under 20A, and I think the kilns are all under 50 A.
The RIBXGTA is ~ $45, but there are cheap Chinese equivalents with dry relay contacts for under $20 on Amazon and fleabay.
SoâŚdoes our unit have (or would @Robert_Davidson like to make one that does & weâd be willing to beta it?) with a plug-out to light up a light. Customer can decide which kind(s) of light(s) are illuminated and where theyâre placed. Or at the very least, that sounds like a good thing for anyone working interlock projects to consider. If the device is already monitoring for power on, let the âcustomerâ use that to their advantage. In the event of this being a commercial venture, perhaps provide some alternative add-ons in the way of plug-in devices that easily meet the power requirements, etc.
probably a wraith thought, but out it spilledâŚ
Iâm working in the interlock sig on this very subject. At the moment, all Iâve considered is an indicator showing that power is applied to the client machine and not whether itâs on or not.
This doesnât exist on most of the interlocks at DMS, and the exception (Lift) is pretty much invisible (dim, on the top of the box - too bad if you are short!, muticolor with no indication of meaning.) This isnât a jab at the original builders, itâs the benefit of 20-20 hindsight. It was clearly on thier mind based on seeing what was stubbed out in hardware and not implemented, or in the code.
This wouldnât be a difficult feature to add, but Iâm always concerned about the âCreeping feature creature.â I need to give it some more thought and solicit some more opinions.
We need to be careful to keep this simple and not have too many lights, flash states, bells, whistles, dancing girls (and guys) and gilt edges. More seriously: my main concern is about reliably informing the operator about issues impacting normal and safe operation. The answer merts careful thought about the whole problem.
@ESmith might want to see this as well.
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The interlock boards already relay 12V DC power out by design.
You can easily add a 12v light of anything you want from a flashing red light that spins or just a simple LED.
Just chose what light you want.
Robert
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Pretty sure Iâve got nothing to do with interlocks, however the previously-involved Robert Davidson has seen and responded to this.
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