If you do maybe you can give me some guidance. I would like to be able to measure the torque required to drive taps so that I know when the tap is getting dull. The torque range is from .5 to 106 inch lbs. The sensor needs to be very low power and the sensor/reader package needs to cost less than $100.00. Is this possible? I am thinking about a MEMS sensor that is powered like an RFID so that there is no contact. The signal from the sensor will then be sent by radio to a receiver less than 15 feet away. I have been looking online but haven't yet found what I'm looking for. Thanks, Eric
It's been decades since I used strain gages, but I suspect the basics are still true. At the most elemental level you have naked strain gages (or whatever technology) that have to be bonded to the part you are applying the torque or load to, then calibrated. Big PITA.
Then you have ready-made sensors that have the strain gages already bonded to a nice torque- or load-sensing structure, with raw bridge outputs, or with built-in electronics. The latter is surely what you want.
The issue becomes whether you can find a ready-made type that you can easily incorporate into your setup... it need to handle the right torque range, of course, but it also needs to physically fit and be easy to couple between the driver and tap.
Sometimes the attachment issue can overshadow everything, forcing you to revert to bonding raw gages to strangely-shaped parts. But I suspect in your case you will be able to find a ready-made sensor.
Have you considered some sort of "proxy" method, such as measuring drive motor current? I'm guessing that you don't really need torque measurement as such, just some corresponding thing that you can detect when it goes above some threshold.
Best regards,
Bob Masta DAQARTA v7.60 Data AcQuisition And Real-Time Analysis
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Scope, Spectrum, Spectrogram, Sound Level Meter Frequency Counter, Pitch Track, Pitch-to-MIDI FREE Signal Generator, DaqMusiq generator Science with your sound card!
When first confronted with this problem, I envisioned a torque measuring shaft wih sometype of vernier scale you could view, then synchronously 'flash' the optics to look at the vernier scale as it rotates during use. Manual reading not electronic, but simple - maybe.
The other technique was again to use shaft torque angle displacement, use YOUR soundcard software to drive a rotating coupled transformer winding in top, pick up the small angular offset to phase sensitive winding in 'bottom' and pick that up wirelessly too. That is four independent windings in all.
But measure current? Never occurred to me. Worst part of this is that back in the 70's we had this problem with dullin milling bits, and the solution, yes measure the current! Actually power, but same principle. oh how quickly we forgeet.
You no longer need to think... just use a microprocessor >:-} ...Jim Thompson
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| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: skypeanalog | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
Took me a while to get used to replacing $20 worth of analog parts with $1 PIC, or $5 FPGA that to add insult to injury actually would outperform the analoog design.
If you chuck the tap in a battery drill/driver, you can just adjust the torque limit, so a dull tap 'clicks' instead of rotating. Or, you could put a torque-limit screwdriver mechanism in a suitable tapping jig. The downside, is that most drill/driver mechanisms will jerk your hand sideways (and break the tap).
A straight-cylinder battery torque-limiting drill would be perfect (you'd still have the feel of the torque, and could let the cylinder slip in your hand instead of snapping the tap). Alas, I don't know of any such.
The biggest problem in using a microprocessor where an analog circuit can do the job, is that the guy designing the system -- circuitry AND code -- needs to understand analog electronics. If it's going to work well, the microprocessor just becomes a custom analog component. Not everyone can do that.
There are still places where analog is a must-use, though.
And as I said to Jim, in a lot of cases, when you replace analog electronics with a micro, you still need to have analog chops to make it all work. When you go ADC -> micro -> driver -> power FET, you'd better understand the care and feeding of the power FET and whatever it's driving.
--
Tim Wescott
Wescott Design Services
http://www.wescottdesign.com
Yup. Almost always there's A-to-D, then D-to-A ...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: skypeanalog | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
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