How-to: Build Your Own Spot Welder

June 23, 2009 by Steve Watkins 85 Comments

Spot welders are used in the fabrication of automobiles, PC cases, power supplies, microwave ovens, electrical junction boxes, Faraday cages, and various electronics. A spot welder is used because it produces a highly defined point of contact weld. The materials are welded without excessive heating, so working pieces are handled easily. The weld is also highly controlled and repeatable. In this how-to we cover the basics of a spot welder, and then show you how to build one from a microwave oven transformer.

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Homemade Toroid Winder

June 20, 2009 by Steve Watkins 17 Comments

[eclipsed78], built an automatic toroid winder (Internet Archive). The drum splits in order to load the toroid. Then wire is wound on the drum, much like any other coil would be wound. The drum rotates as a slider pulls the wire off the drum, while revolving in and out of the toroid. A side tension keeps the slack out of the wire during operation. The winding coil is stepped as the drum rotates, in order to control the turns ratio. [eclipsed78] created a stepper driver from a schematic, so he could drive the motors. You can watch the winder in operation as a series of videos. The first of which is embedded below. If you have ever needed to wind a massive toroidal transformer, this is the project for you.

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Parts: Programmable Gain Amplifier (MCP6S26)

March 30, 2009 by Ian 12 Comments

mcp6s26

Microchip’s MCP6S21/2/6/8 are programmable gain amplifiers that multiply an input voltage by a factor of 1, 2, 4, 5, 8, 10, 16, and 32. The MCP6S22/6/8 also have selectable input channels for working with different signal sources. The multiplication factor and input channel are configured through an SPI interface. This chip is useful for multiplying a small input signal, and selecting among several analog input sources. We demonstrate the six channel MCP6S26 below.

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Parts: DS1801 SPI Audio Volume Potentiometer

March 16, 2009 by Ian 3 Comments

ds1801

Dallas/Maxim’s DS1801 is an audio volume potentiometer with a simple SPI interface. This chip has two channels of volume control that might be useful in a DIY audio project. We previously looked at the DS1807, a similar part with an I2C interface. This week we’ll show you how to use the SPI version.

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Parts: 4×4 RGB Button Pad Controller SPI

March 9, 2009 by Ian 2 Comments

We covered SparkFun’s new RGB button pad controller a few weeks ago. This is a full-color clone of the monome interface; a 4×4 grid of buttons with tri-color LEDs underneath. Each LED has 24bits of color control, for more than 16million color combinations. Up to 10 panels can be chained together to create huge button grids, like SparkFun’s Tetris table. We previously used a smaller version in our RGB combination lock.

We asked SparkFun to send us the SPI version of the button controller to test. This is a new product developed in-house at SparkFun, with open source hardware and software. Read about our experience interfacing this board below.

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Parts: 32KB SPI SRAM Memory (23K256)

March 2, 2009 by Ian 15 Comments

23k256ii

Microchip’s new 23K256 is a serially interfaced 32 kilobyte SRAM memory chip, available in 8 pin DIP and 8 pin SO packages. SRAM, like EEPROM, is a data storage medium. Data stored in SRAM is lost without constant power, but it’s really fast and there’s no limits to the number of write cycles. EERPOM stores data even without power, but it’s slow and usually limited to around a million write cycles.

32K SRAM chips typically have 15 address lines and 8 data lines, like the IS61LV256AL we used on our CPLD development board. The 23K256 requires just four signal lines, but sacrifices the speed of a parallel memory interface. It’s a great way to add extra memory to a low-pin count microcontroller without routing 23 signal traces. We’ll show you how to interface this chip below.

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Parts: I2C Audio Volume Potentiometer (DS1807)

February 16, 2009 by Ian 7 Comments

ds1807ii

The DS1807 contains two logarithmic digital potentiometers (pots) for audio volume adjustment. Each pot has 64 volume levels plus a mute setting. The volume level of each pot is set over a two-wire I2C serial interface. We’ll show you how to connect and interface the DS1807 below.

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