DIY

Using Hobby RC parts in DIY projects

4volt — Sat, 05 Jun 2010 09:29:33 GMT

I’m always happy when I find a new kind of part that is cheap and easy to use with DIY electronics projects or robotics, the more standardized the better.

There’s a whole world of smart electronics and helper things in the hobby and remote control world that are great for robots and other things.

You probably already know that hobby servos are easy to control from any microcontroller like the arduino, but there are a bunch of other things that are just as easy to use. Generic motor controllers, battery systems are also equally as useful, but are sometimes hard to sort out the jargon and acronyms that R/C hobbyists use.

Some of the terms are pretty confusing, and a lot of acronyms and other R/C only rating systems are used. I’ve made this short reference to make it easer to sort out what all those things mean. I've found myself wondering more then once what the difference between an ESC and a BESC, or what a 2S2P 10C battery is.

Power / Voltage Regulation

ESC
(Electronic Speed Controller)

Uses a PWM signal to control the speed of a motor
ECS’s are made for either brushless or brushed motors (See motors)
ESC's are rated in Amps (A) for how large of a load/motor they can control

BEC
(Battery Eliminator Circuit)
Steps a higher voltage down to a lower voltage, a kind of voltage regulator
UBEC
(Ultimate BEC)
Same as a standard BEC, but made for higher voltages
BESC
(Battery eliminator speed controller)
An ESC with BEC
LVC
(Low Voltage Cutoff)
Keeps LIPO batteries from becoming too drained, which can be dangerous, usually a feature of a controller
DVM
(Digital VoltMeter)

Controller Acronyms

RX – receiver

Receives a control signal from the transmitter, output's a PWM signal for servos or speed controllers

TX – transmitter

(The remote you hold in your hand)

Battery Terms

LiPo, LI-PO, Li-Poly
Short for lithium ion polymer battery, the standard type of R/C battery
LiFe - LiFePO4
Lithium Iron Phosphate battery, generally safer then LIPO batteries, better shelf life, faster charging
NiMh
Cheaper, but generally not as good as LiPo or LiFe
S Rating (Like: 1S, 2S, 4S, 6S, etc)
Number of cells in a battery pack
A single LiPo cell is 3.7v
A single LiFe cell is 3.5v
A single NiMh cell is 1.2v
P Rating (Like: 2P, 4P, etc)
Number of parallel lines in the battery, each parallel doubles the mAh the battery can deliver

A 2S2P battery has 4 cells in 2 parallel lines
C Rating (Like: 1C, 10C, 20C, etc)
Amount of current battery can discharge in an hour
1C = Batteries entire capacity

A 10C, 500mAh battery can discharge at 5,000mA (5A) max, and have about a 6 minute life at max discharge

A 20C, 500mAh battery can discharge at 10,000mA (10A) max, and have about a 3 minute life at max discharge
Charging Bag, Charge Pack
A fireproof safety bag for storing batteries
LIPO Monitor
An alarm that goes off if the battery voltage drops too low. Batteries that drop too low can be damaged, or possibly explode.

Motor Terms

Brushless Motor
A motor that runs off of A/C power, and has no "brushes" that transfer current into the rotating spindle. Brushless motors are similar to stepper motors, but only have two coils.
Brushed, Canned, Standard Motor
A traditional DC driven motor
Coreless motor
A motor without the iron core in it's windings
Outrunner motor
Brushless motors where the casing spins and the center stays still

Motor is mounted by the back of the shaft
Low RPM's, high torque
Silent

Inrunner motor
Brushless motors where the center core spins, and the casing is fixed

Motor is mounted by motor casing
High RPM's, low torque
More efficient than outrunners

GB
Gear box, usually for planes
KVM, kv-RPM, KV
A motors' RPM in thousands per volt supplied

Servo Terms

KG Rating (Like: 10kg, 20kg, etc…)
Amount of force the servo can exert in kg/cm
Can also be rated in oz-in (Imperial)
G Rating (Like: 30g, 50g, etc…)
How heavy the servo is
Can also be rated in oz (Imperial)
Sec Rating (Like: 0.20sec, 0.50sec)
How fast the servo can rotate in seconds (usually for 60 degrees)
Digital Servo
Pretty much like a non-digital servo, but uses a microcontroller brain

Testing Jansen Walker Version 3

4volt — Mon, 15 Feb 2010 23:03:04 GMT

Over the last week I’ve been working on the next version of the Jansen Walker, this will be the 3rd release.

The goal is to make it much easier to assemble, faster, and 1/3rd larger using 3mm (1/8in) material.

The biggest change is that instead of using modified servos, which seem to scare a lot of people off, use geared motors which are about the same price. That will make the electronics side easier, perhaps slightly more expensive depending on your controls.

The new version will use the Tamiya Twin-Motor Gearbox, that has a good 203:1 ratio that is ideal for a medium to low RPM walker. It’s $10.95 at SparkFun.

I see three obvious ways to control the walker electronically:

Very simple: switches and batteries
Direct wired buttons to the motor and battery would work well, but have no speed control
A generic R/C setup with a remote, receiver, and two small speed controllers. I think this would be fun.
An arduino or any microcontroller with a motor shield

I’m also playing around with ideas to make assembly easier and faster. Currently it takes about 4-6 hours to assemble, mainly because of all the legs and joints. There are 5 joints per leg, and there are 12 legs.

The next thing I'll be trying is nylon tubing and compression using bolts, that should allow for secure joints that still still rotate freely. As soon as my parts arrive I’ll be testing this method, I think it will shorten assembly time by as much as half.

Laser Toy Blocks

4volt — Sat, 06 Feb 2010 09:26:09 GMT

For Christmas this year I made some custom toy blocks with friends and family initials.

The blocks were cut from square wood stock into 1.25in cubes. The stock I used was indented for banisters, and had peg ends, but they were easily cut off.

I made a batch of both Oak and Fir. Oak turned out fine, and is what is pictured here. The Fir blocks came out with a more slightly more desirable finish since the end grain was more smooth after sanding.

Setup

First I taped down a 3mm (1/8th in) board and cut the appropriate number of squares at the same size as the blocks.

Cutting a grid instead of a single square helped to keep each block in the right spot for engraving.

The last task was to choose the fonts that would appear on each side of the block then lay out 6 versions of the same letters but different fonts to engrave on each side.

I chose some initial fonts from dafont.com, choosing the fonts was half of the fun.

Packing

I made a custom version of my original papercraft folded box, check the included zip file for a box that fits 3 1.25in blocks perfectly (33x99mm).

The “Cheap and Easy” Photo Backdrop

4volt — Mon, 11 Jan 2010 08:50:00 GMT

Every now and then everyone needs to take a photo of something small, there’s an easy (and cheap!) way to get a great looking photo with a white background.

As soon as you see the technique, it’s hard to forget, it’s a plain white poster board propped up against a wall or whatever you have handy. Fill your camera’s view with the poster board and take the photo.

For lighting you’ll need a reflected flash or some bright lights, but that is not the focus of this article. I’ll soon do an article on my flash bouncer.

Below are a few photos of the setup, it’s easy to understand once you see it in action.

This technique works great for smaller items that are not too shiny. If the item is too big, you’ll have a tough time covering the edges.

If the item is shiny you’ll be able to see in the reflection of the object the rest of your room and camera. For those kinds of things a light tent would be better. (and more costly)

Holiday Post-mortem

4volt — Mon, 04 Jan 2010 09:26:56 GMT

The holidays are a undoubtedly a a big cost every year for me, but this year I decided to try something different, I wanted to make all my gifts, or give things that are new but unused. My quest was a success, I effectively bought no new packaged items. I did buy some raw materials, but no packaged things.

Thingiverse.com was a big help, and I also produced a few things I designed, including:

Earphone Holder by 4volt

Gothic Bookends by 4volt

Little Business Card Stand by oomlout

DIY iPhone stand... by ptorrone

Crosslink ellipse gears by stickoutrock

I used my new envelope design to make a nice package for these small items, I printed on letter sized cardstock, then cut the envelope out of the printed stock. The result was very nice and I think people were impressed. They were great party favors, and for bigger gifts I included 2 or 3 three different items along with the these engraved blocks shown next.

For a more personalized gift I made these personalized wood blocks with ornate letters with monogram initials. I’ll also be posting details on these soon.

So stay tuned for more cool stuff, as usual.

Thing: Earphone holder (folding style)

4volt — Fri, 18 Dec 2009 22:31:33 GMT

For Christmas this year I’ll be giving out inexpensive things I’ve cut with my laser, here’s one of the original designs I’ve come up with, a small holder for earbud style earphones.

Other earphone winder designs make you wrap your chord around and around until you’ve wrapped the whole chord. That way is pretty aquard, and I never end up using them. It really is quite a bit faster to “fold” then to “loop”.

This winder/holder is designed for that with a hook on one side, and a strap in the middle. Although, you can still wrap them the other way of you prefer.

How to use:

Start with both ends of the earphone in one hand
Fold the far end into your hand with the ends
Keep folding until the length of the fold is about twice the length of the holder. Also, try to keep the loop clear so that there is a good loop to hook in the next step.
Hook the loop on the center prong of the 3-prong side
Loop the bundle around to the far side of the holder, and strap the bundle down with the Velcro.
Finished!

This method of folding should only take about 15 seconds (or less!) once you’ve done it a few times. Once it’s wound, it’s quite compact and fits in a pocket easily.

A note about cable strain: When your are strapping your bundle down, it should be tight enough on the ends that it doesn't slip off the holder, but still a little loose. Use the Velco to keep it all together.

Download the files to make your own: Zip File (2.2mb)

Or send me a donation, and I’ll mail you one to say thanks!

Making a $1,000 laser into a $10,000 laser

4volt — Tue, 17 Nov 2009 19:57:25 GMT

If you follow this blog you’ll know I do a lot of stuff with my cheap $1,000 dollar Chinese laser engraver/cutter. I’ve had it for almost a year, and I think I can clearly define all it’s shortcomings.

Cutting area is small (8x8in)
Controller software is poor
Laser power control is manual
Poor ventilation for fumes
Poor/no laser cooling system
Not very fast with engraving tasks

Keeping all those things in mind, I’ve decided to start planning a re-build of my laser using existing and new parts, and a case/frame.

I'll use a generic step/gcode controller for the movement, there seems to be many generic controllers of this type that could be controlled with PWM step code (mach3) or serial gcode.

For axises, there would be the regular X and Y for "standard" laser movement, a powered (low speed) Z for table height, and an optional rotational axis for the round materials adapter.

Additionally, will be a PWM control for the lasers power and the air assist, probably from a separate controller that may be custom.

All settings will be computer controllable, so that eventually when I have time to write some software, I can make a material preset manager to adjust the table, air and power for specific saved materials.

Eventually, I would like to have a job template system that has all the settings for a job that would adjust the general settings and start cutting by simply selecting a saved job. This is probably a long way away, but I'm keeping it in mind while planning.

The new box will be about 640mm deep (25in), 540mm tall (21in), and about 800mm wide (32in). The cutting area, will be somewhere in the range of 400x600mm (16x24in), possibly a bit larger depending on how large a few of the components end up being once I've designed them.

The machine will be split into two parts, the top and the bottom. In general the electronics and laser tube are in the bottom, and all the cutting bed is in the top. That makes the machine taller, but allows a much larger cutting area without hugely increasing the footprint. That design will require one extra mirror.

The frame will use 20mm and 40mm 80/20 (t-slot) aluminum extrusions (See 8020.net). It is easy to work with and does not require very many tools or welding to build with, also looks cool.

After all that planning and work, I hope to have a laser engraver that is comparable with the more expensive/convenient versions that are out there now. Keep tuned for more updates in the coming months.

Project: Gothic Architecture Bookends

4volt — Wed, 23 Sep 2009 16:19:00 GMT

With the glorious re-launching of my laser, I broke it in with a new design. This is a design meant mostly for small books and is inspired by Gothic Architecture.

This is a design meant mostly for small books and is inspired by Gothic Architecture, inspiration drawn from Cologne Cathedral, and Church of St Barbara Kutna Hora. There are several flying buttress and the "windows" are done in the style of a Flamboyant arch. The small gargoyles are designed after the hunched Notre Dame gargoyles.

Lately I've been doing mostly mechanical projects, there satisfying to build, but usually very time consuming. This project turned out pretty good, and was a quick turnaround, I went from idea to physical thing in the same day.

As usual the files to make your own are over at the project page, check it out. You can also buy a set over on the Donate page.

Laser GO!

4volt — Tue, 15 Sep 2009 18:35:29 GMT

After a few weeks of having a broken laser, I received my replacement laser power supply and installed it last night. I emailed a few sellers on eBay that sold similar looking laser engravers with pictures of the fried parts, and I was able to fine someone that happened to have a spare and ships from the US.

I was a bit worried about screwing something up, the red power lead you see coming out of the transformer is soldered directly to the laser tube’s terminal. Connecting the new lead was a bit cumbersome with limited space, but not difficult. The new supply fit perfectly in the old place and I did not have to modify any mounting holes or even figure out what unmarked wires served what purpose since all the connection points were exactly the same.

All in all the replacement took about an hour and the laser just worked with no debugging or hassle with the new part.

The biggest worry I had when I originally bought this laser was that if anything broke down I would not be able to find replacement parts. While you probably can’t find any parts locally, there seems to be plenty of places online that can get the parts.

Hex Toy 3mm –or- 1/8in

4volt — Thu, 25 Jun 2009 07:16:32 GMT

If you are not familiar the Hex Toy is a laser cut building toy, the edge notches fit together to make abstract shapes.

Here’s a new version made specifically made for 3mm and 1/8th in plastic. The notches are larger, and the peices themselves are larger too. The feel is much more substantial.

Check out the Hex Connectors project page for more detail and to download the new design.