Retrotechtacular: Synchros Go To War (and Peace)

Rotation. Motors rotate. Potentiometers and variable capacitors often rotate. It is a common task to have to rotate something remotely or measure the rotation of something. If I asked you today to rotate a volume control remotely, for example, you might offer up an open loop stepper motor or an RC-style servo. If you wanted to measure a rotation, you’d likely use some sort of optical or mechanical encoder. However, there’s a much older way to do those same tasks and one that still sees use in some equipment: a synchro.

The synchro dates back to the early 1900s when the Panama Canal used them to read and control valves and gates. These devices were very common in World War II equipment, too. In particular, they were often part of the mechanisms that set and read gun azimuth and elevation or — like the picture to the left — a position indication of a radar antenna. Even movie cameras used these devices for many years. Today, with more options, you don’t see them as much except in applications where their simplicity and ruggedness is necessary.

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Friday Hack Chat: A Design Slam Challenge

Every Friday, the community gathers ’round the fireplace and discusses the challenges facing the world. This is the Hack Chat, and in previous incarnations, we’ve talked about custom silicon, Arduinos, PCB fabrication, old technologies, and hardware manufacturing.

For this week’s Hack Chat, we’re opening up a design challenge. We’re asking the community for help on developing a wireless position sensor. This is a Design Slam Hack Chat, and we’re looking for contributors.

Our guest for this week’s Hack Chat will be [Naveen Nair], technology leader for GE Fuse. We’ll be discussing position sensors during this Hack Chat. If you’ve ever used a mouse, you’re using a position sensor, but for this Hack Chat we’re designing something a little more challenging. The Fuse group is attempting to build a low-cost, wireless position sensor with hand-held ultrasonic inspection units. Why is GE interested in this technology? Our guess is inspecting jet turbines, or something like that. That doesn’t mean low-cost wireless position sensors wouldn’t have other applications, though. Just imagine what a quadcopter could do if it could sense its position with 1mm resolution.

Won’t be able to make the Hack Chat? Don’t worry, we’ll be putting a transcript up here sometime after the event.

Here’s How To Take Part:

join-hack-chatOur Hack Chats are live community events on the Hack Chat group messaging. This Hack Chat will take place at noon Pacific time on Friday, July 7th. Confused about where and when ‘noon’ is? Here’s a time and date converter!

Log into, visit that page, and look for the ‘Join this Project’ Button. Once you’re part of the project, the button will change to ‘Team Messaging’, which takes you directly to the Hack Chat.

You don’t have to wait until Friday; join whenever you want and you can see what the community is talking about.

I’ll See Your Launchpad Controlled Arm And Raise You Arduino Controlled Autonomy

This OWI robot arm has been hacked to add position sensors and Arduino control. [Chris Anderson] took one look at the Launchpad controlled OWI from earlier today and said “wait a minute, I’ve already posted my own version of that project”. Well, that will teach him not to tip us off about his hacks!

The position control is a really nice addition. Potentiometers added to each of the joints (shoulder, elbow, and wrist) can be read by the ADC pins on the Arduino. Just a bit of calibration will let the microcontroller board know the position of the arm at any given time. The control technique is the same as the Launchpad hack, with one glaring drawback. [Chris] is using the Adafruit motor driver shield. It uses L293D H-bridge chips, but it only has four channels. There are five motors on this arm, so the video after the break shows it moving around without any outside instruction, but you won’t see it grab onto anything since the Arduino can’t move the gripper!

Still, the position feedback makes the case for this version. Just remember to order an extra chip if you want full control.

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