Reverse Engineering LCD Displays

Dorkbot logo on a large LCD display

Over at DorkbotPDX in Portland, a member showed up with a stack of large LCD displays from point of sale terminals. [Paul] took it upon himself to reverse engineer the displays so that they can be recycled in future projects.

The control circuit for this LCD resides on a rather large PCB with quite a variety of components. The board was reduced to three main components: an MSM6255 display controller, a 32k RAM chip which is used as the framebuffer, and a tri-state driver.

With all the unneeded components out of the way, a custom board based around an ATmega88 MCU was added. This board was soldered in to interface with the LCD controller’s bus. This allows data to be written from the 128k flash ROM on the custom board into the frame buffer. Once this is done, the display controller will display the data on the LCD.

Now that data could be written, [Paul] figured out the correct configuration for the display controller. That was the final piece in getting images to show up correctly on the display. If you happen to find some old Micros 2700 POS terminals, [Paul]‘s detailed write-up will help you scavenge the displays.

LEGO® My Single-Phase Induction Motor

[Diato556] made a really cool single-phase induction motor with parts mounted on Duplo blocks. He has posted an Instructable where he uses these modular parts to  demonstrate the motor and the principles of induction as described after the jump.

 

[Read more...]

The Beginnings of an LCR Meter

LCR Meter

The inductor is an often forgotten passive electrical elements used to design analog circuitry. [Charles's] latest proof of concept demonstrates how to measure inductance with an oscilloscope, with the hopes of making a PIC based LCR meter.

It is not that often one needs to measure inductance, but inductors are used in switching regulators, motor circuits, wireless designs, analog audio circuitry, and many other types of projects. The principles of measuring inductance can be used to test inductors that you have made yourself, and you can even use this knowledge to measure capacitance.

[Charles] originally saw a great guide on how to measure impedance by [Alan], and decided to run with the idea. Why spend over $200 on an LCR meter when you can just build one? That’s the spirit! Be sure to watch [Alan's] and [Charles's] videos after the break. What kind of test equipment have you built in order to save money?

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Direct, Wall-Mounted Storage with Lasers and Polymorph

parts-storage-brackets

We’re sure everyone could use some more storage and organization in their workshop. [Nixie] is no exception, though he also hates sacrificing tabletop space for boxes. His solution was to attach them to the wall directly by hacking together some brackets. This hack allowed him to hang everything without using internal screws which were a pain to get at if he need to removed the boxes from the wall to take with him.

[Nixie] started by laser-cutting a negative pattern for a mounting bracket that would fit the dovetail rails already on the sides of the boxes. He then pressed a piece of polymorph into this mold, slid the bracket along the side of the box…and realized it wouldn’t work. The piece wiggled around too much because it did not sit firmly in the rail. Back at the drawing board, [Nixie] split the project into two steps. He cast the screw-hole portion of the bracket in its own separate mold, then cast the railing part of the bracket directly in the dovetail section of the box, providing him a much higher degree of accuracy. After joining the two pieces, [Nixie] had a sturdy support bracket that he duplicated and attached around the rest of the bins.

FT230X Brings USB Charging Detection to the Serial IC Game

FT230XS-breadboard

Here’s a new chip from FTDI which brings a nice little feature to the USB-to-serial converter family: charging detection. That means that it is capable of detecting when a battery charger is connected. What does that actually mean? The top of the datasheet gives you the short version, but let’s look at the investigation [Baoshi] undertook to test the full extent of this particular feature. We agree with him that the listed capability leaves those in the know with a lot of questions:

USB Battery Charger Detection. Allows for USB peripheral devices to detect the presence of a higher power source to enable improved charging.

Obviously the chip will be able to tell when a charger is connected, alerting the device when it’s time to start lapping up the extra milliamps. But what type of chargers will actually trigger the detection circuit? After rigging up the test circuit shown above he ran through several scenarios: connected directly to the PC USB port, via externally powered and non-powered USB hubs, and with multiple wall wart chargers. Full results of the tests are included in the post linked above.

[via Dangerous Prototypes]

Maxim App Note Reuses Lithium Ion Cells — Plus Extras

maxim-reusing-old-lithium-ion-batteries

Now we don’t sit around reading application notes for fun. But if hard pressed we would have to admit that we do read quite a few of them even if the concepts aren’t currently on our project list. That’s because they’re a great way to learn stuff and for the most part the information within is trustworthy.

The latest one that we looked at is this Maxim app note 5681 on recycling Lithium-ion batteries. It’s more a reuse than a recycle but you get the point. If you have some Lithium-Ion cells left over from older equipment this resource delivers a lot of good information on how to use them to power something else.

Obviously they’re showing off their own hardware here, but that’s okay. The MAX8677A chips has a ton of features and can be had for $3-5 depending on your vendor. It automatically switches between powering your device from the battery, or from the charging source if connected. This allows you to source up to 500mA when connected to USB or 2A when charging from an external DC supply. There is also all of the protection you would normally want with a Li-ion setup, including temperature monitoring.

The catch is the not-so-hand-solderable QFN package. They’ve got a solution to this as well. The diagram on the right shows how to hand solder the chip — albeit with a hot air pencil — by drilling through the board to get at the ground pad from the underside of the PCB.

[Thanks Jaded and Amos]

One man’s microwave oven is another man’s hobby electronics store

Mads microwave teardown

There are loads of Internet content depicting the usefulness of salvaged innards found in defunct microwave ovens. [Mads Nielsen] is an emerging new vblogger with promising filming skills and intriguing beginner electronics content. He doesn’t bring anything new from the microwave oven to the dinner table, yet this video should be considered a primer for anybody looking to salvage components for their hobby bench. To save some time you can link in at the 5 minute mark when the feast of parts is laid out on the table. The multitude of good usable parts in these microwave ovens rolling out on curbsides, in dumpsters, and cheap at yard sales all over the country is staggering and mostly free for the picking.

The harvest here was: micro switches, X and Y rated mains capacitors, 8 amp fuse, timer control with bell and switches, slow turn geared synchronous 4 watt motor 5 rpm, high voltage capacitor marked 2100 W VAC 0.95 uF, special diodes which aren’t so useful in hobby electronics, light bulb, common mode choke, 20 watt 68 Ohm ceramic wire-wound resistor, AC fan motor with fan and thermostat cutout switches NT101 (normally closed).

All this can be salvaged and more if you find newer discarded units. Our summary continues after the break where you can also watch the video where [Mads] flashes each treasure. His trinkets are rated at 220 V but if you live in a 110 V country such components will be rated for 110 V.

[Read more...]

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