I designed and built a solar hot water controler back in the early 80's. It is also of analog design and built and tested to UL standards. I built a total of 50 units, all of which are still operating (to my knowledge) to this day. No one has complained. Several of them, including mine, had to have the wires to the panel sensor replaced due to UV damage. The pump is controlled using a TRIAC in place of a relay. Troubleshooting and replacing defective components is easy on the double-sided board, and parts are still available to this day.
I had a simular experiance with my solar pool heater. The controler stopped working, I removed the controller from the circuit and found the power relay tha operated the water valve was defective. I went on line to find the part. The venders had a $50 mimium order so it was prohibitively expensive so I bought a new control;ler for $100. Problem solved!
Reminds me when I had a VW Diesel Rabbit. The car ran well, but one time a water leak got in the glow plug time delay relay. It failed and I had to lift the hood and apply a jumper between the battery and the glow plug bus for 30 seconds or so to get the car started. I checked the VW dealer and a new plug in relay was $35 a lot in 1985. So I took the old relay apart, and replaced the comparator ICs, which cost less than $1 each, but with shipping ended up costing $4. It was good for the rest of the car's life.
I'm watching my favorite program and there is a knock on the door. My neighour needs leads for his multimeter. I lend him the whole Harbour Freight special with clamp on ammeter with a breif explaination.
Then I think, he knows enought to to pull the plug, right. He is trouble shooting his electric dryer. I had to check. Yes, he knows. We looked a lot of the part. The schematic used non standard symbols but we figure out what was what.
I mensioned that what works is as important was what does not work. It does not do any thing. Oh, yes the door light comes on and the clock works runs. I showed him how to jumper around components. I explained the schematic some what. With a half hour we found the thermal limit component that we jumped allowing the other phase to power the motor.
He went on line and found the component. He phone a friend in the business who had the part. He replace the part and had the dryer running about an hour and half after I started.
He thinks I should go into the business. I think it could never pay enought fixing things rather than Oh its broke and cant be repaired I'll sell you a new one. Just too honest. An not worth my time. But it was fun.
I forgot to mention the Mitsubishi ECM (car engine control module "computer") which needed four inexpensive capacitors and some jumper wired where PCB traces had been eaten through by poorly-selected capacitor adhesive. That baby would have cost $700, had I not been able to install about $4.75 worth of capacitors.
And the dishwasher control which was over $12, but not available, fixed with a couple of "bullet" connectors costing pennies.
And I already promised to write you about the GM high-mounted brakelights. They will have to be a destructive analysis. I tried to open them to effect a repair but they were bonded (ultrasonically welded? epoxied?) so well that I will have to break them apart to find out what failed.
Terribly busy right now--besides my day job I'm leading the volunteer recovery effort from the tornados which struck here on April 16, 2011. This consumes all my nights, but it's nearly done. I should be able to send you something in May or June.
We'd love to use some of your stories at Sherlock Ohms postings. Could you send one or two of them along? They need to be at least 350 words, and we also need a shor bio to go along with it -- about two to four sentences would be find.
I've lost track of all the non-user-serviceable products and components I've fixed.
There was the PC motherboard which wouldn't drive the printer. Had to replace a surface-mount IC on it.
The 1984 washer that was incredibly robust but stopped working in 2008. It would never progress from the washing cycle to drain, fill, and rinse. The controller board would have cost $350, except you couldn't even get them. The triac which fixed it cost 37 cents from Mouser.
Two Roombas, each of which had failures in the battery charger. Each took two surface mount transistors (didn't bother to figure out which one had failed).
The loss of innocence of my son, at about age 12: "Dad, this stereo receiver is dead. It won't go on. Nothing at all." "Son, get a #2 Phillips screwdriver from the workbench." "Dad, the label says 'No user serviceable parts inside.'" "Yes, son. no user serviceable parts inside." as screws are removed from the cover. "Son, no user serviceable parts inside," as the cover is lifted off, revealing a blown glass cartridge fuse in clips, in plain sight at the top of the unit.
My son is now 37. I'm still using the receiver, haven't had to change the fuse a second time yet.
The $1.50 picofuse that put the $200 laser printer back into service in 2005 or so. Still using it.
There are dozen more instances, but they all follow the same pattern. If you simply think a little, you can replace inexpensive components instead of expensive assemblies or complete products.
Andrew Morris designed a circuit that could detect a stroke victim's groan and convert the sound into a signal so caregivers would know when help was needed.
New disc magnet motors fit into the design trend of stepping up to closed loop performance while maintaining the cost advantage of stepper motor technology.
At the Design News webinar on June 27, learn all about aluminum extrusion: designing the right shape so it costs the least, is simplest to manufacture, and best fits the application's structural requirements.
On April 21, NASA launched a novel project, putting into orbit three satellites that employ an off-the-shelf commercial smartphone as the control system.
From Dell / Intel® New Paradigms in Design Work Scott Hamilton, vertical market strategist for Dell Precision workstations, 5/2/2013 5
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For industrial control applications, or even a simple assembly line, that machine can go almost 24/7 without a break. But what happens when the task is a little more complex? That’s where the “smart” machine would come in. The smart machine is one that has some simple (or complex in some cases) processing capability to be able to adapt to changing conditions. Such machines are suited for a host of applications, including automotive, aerospace, defense, medical, computers and electronics, telecommunications, consumer goods, and so on. This radio show will show what’s possible with smart machines, and what tradeoffs need to be made to implement such a solution.
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