Skip to main content

DIY Roomba Virtual Wall, Part 3

I created an enclosure for the ATtiny85-based Roomba virtual wall prototype board using FreeCAD.

A couple of design goals:

  • The LED is positioned about 7cm from ground level.
  • The 3 x AA battery holder is 3D-printed, completed by battery clips salvaged from old toys (or readily available online).
  • The parts are designed to print with as little support as possible, and attached together using superglue and screws.

I printed the parts using 0.8mm nozzle to save time, so they look a little rough. It takes about 7 hours to print all the parts on my Creality Ender 3.

Nine M2.5 screws are required, one for the battery cover, eight for holding the body together. Superglue can be used for the latter, but I like the option to easily take the body apart for repair.

Here is the battery box with battery clips inserted:

JST male connector wire soldered at the back:

Mounting clips attached with superglue. When working with superglue, move the parts in position and hold down with pressure for 60 seconds. A small grip clamp is useful for this, otherwise just apply pressure with your fingers. The pressure is very important in order to create a strong bond.

Insert the main body and secure with four M2.5 screws.

Attach mounting clips for top cover:

Attached prototype board with hot glue. Superglue could be used, but hot glue is easier to remove if I ever needed to detach the prototype board:

Prepare the top cover by pushing in the insert:

Attach top cover to body with four M2.5 screws:

The all white body is a little bland, so I made it more noticeable by covering the joints with some 3M electrical tape:

I found the IR LED has a (half) angle of projection of about 30°:


This means having to offset the virtual wall by about 20cm from where you want the actual boundary to be. 

I know the angle of projection is a function of the IR LED, and parts with narrower projection angles are available. But I was wondering if this could be improved by encasing the LED in some sort of cover, so I printed one:

In case you are wondering, it didn't help. But it broke the monotonous outline of the blockish looking unit and made it visually more pleasing (at least to my eyes), so I decided to keep it.

I also tried fitting pieces of straw over the LED, but it didn't help too. Maybe it's because the material of the straw is translucent and does not block enough of the emitted IR.

See it in operation:

I have uploaded the FreeCAD schematic to the Github repository.

Part 1 - Part 2 - Part 4


Comments

Popular posts from this blog

Adding "Stereo Mixer" to Windows 7 with Conexant sound card

This procedure worked for my laptop (Thinkpad E530) with a Conexant 20671 sound card, but I suspect it will work for other sound cards in the Conexant family. I was playing with CamStudio to do a video capture of a Flash-based cartoon so that I can put it on the WDTV media player and play it on the big screen in the living room for my kids. The video capture worked brilliantly, but to do a sound capture, I needed to do some hacking. Apparently, there was this recording device called "Stereo Mixer" that was pretty standard in the Windows XP days. This allowed you to capture whatever was played to the speaker in all its digital glory. Then under pressure from various organizations on the dark side of the force, Microsoft and soundcard makers starting disabling this wonderful feature from Windows Vista onwards. So after much Googling around, I found out that for most sound cards, the hardware feature is still there, just not enabled on the software side. Unfortunately, to

Hacking a USB-C to slim tip adapter cable to charge the Thinkpad T450s

This hack is inspired by this post . A year ago, I bought an adapter cable for my wife's Thinkpad X1 Carbon (2nd Gen) that allows her to power her laptop with a 60W-capable portable battery (20V x 3A). A USB-C cable goes from the battery into the adapter, which converts it to the slim tip output required by the laptop. Everything works out of the box, so I didn't give much thought about it. Recently, I decided to buy a similar cable for my Thinkpad T450s. I know technically it should work because the T450s can go as low as 45W (20V x 2.25A) in terms of charging (though I have the 65W charger - 20V x 3.25A).  I went with another adapter cable because it was cheaper and also I prefer the single cable design. So imagine my surprise when the cable came and I plugged it into my laptop and it didn't work! The power manager just cycle in and out of charging mode before giving up with an error message saying there is not enough power. After much research and reading the Thinkwiki

Attiny85 timer programming using Timer1

This Arduino sketch uses Timer1 to drive the LED blinker: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 /* * Program ATTiny85 to blink LED connected to PB1 at 1s interval. * Assumes ATTiny85 is running at 1MHz internal clock speed. */ #include <avr/io.h> #include <avr/wdt.h> #include <avr/sleep.h> #include <avr/interrupt.h> bool timer1 = false , led = true ; // Interrupt service routine for timer1 ISR(TIMER1_COMPA_vect) { timer1 = true ; } void setup() { // Setup output pins pinMode( 1 , OUTPUT); digitalWrite( 1 , led); set_sleep_mode(SLEEP_MODE_IDLE); // Setup timer1 to interrupt every second TCCR1 = 0 ; // Stop timer TCNT1 = 0 ; // Zero timer GTCCR = _BV(PSR1); // Reset prescaler OCR1A = 243 ; // T = prescaler / 1MHz = 0.004096s; OCR1A = (1s/T) - 1 = 243 OCR1C = 243 ; // Set to same value to reset timer1 to