Category Archives: Uncategorized

Atomic Clock

Here is my new Rubidium Frequency Standard. It’s an atomic clock! It has a crystal oscillator disciplined to Rubidium-87 hyperfine transition.

Rubidium Frequency Standard - Atomic Clock

It has an impressive specification:

Drift 2×10-9/year
Allan Deviation 1.4×10-11 /√ τ (1s ≤ τ ≤ 100s)

I do not (yet) have any means for verifying its stability and accuracy. A quick test with my frequency meter suggests that it is working correctly. However this test does not tell me much as this frequency standard stability is many order of magnitude better than my frequency meter. I am planning to get a GPS disciplined oscillator for performance comparison.


I’ve been experimenting with FTDI FT2232H chip. It is a Hi-Speed USB 2.0 convertor chip. I’ve been operating it in asynchronous FIFO mode and have been able to achieve around 6MB/s transfer rate. Later I will try out the synchronous FIFO mode and hopefully be able to achieve >25MB/s transfer rate as claimed by the manufacturer.

This chip makes building hi-speed USB 2.0 peripheral really easy. I like it!

FT2232H Experiment

Logic analyzer capture showing read and write transfer rate.

FT2232H Logic Analyzer Capture

Arduino Remote Control Infrared Player

This project uses the Arduino hardware for playing back infrared remote control code. The format played is the Pronto Hex format. There is a huge database of infrared code located at RemoteCentral.

I did this project for teaching my learning remote the discrete on/off power code of my TV. The code sent by the original TV remote is the power toggle command. This is not so good when used as part of a macro for controlling multiple devices.

Infrared Remote Control Code Player
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Sparkfun Free Day 2011

Woohoo! I got myself a free $30 voucher from Sparkfun Free Day. Thanks Sparkfun! 🙂

Sparkfun free day is part of Sparkfun’s marketing stunt that started last year where they gave away $100,000 with a limit of $100 per person. This year they increased the amount to $150,000.

I’m not sure $30 is worth the trouble of staying up from 3am to 5am pressing the refresh button on my browser. Anyway I’m happy getting the voucher.

My First Oscilloscope

During clean up I found the receipt for my first oscilloscope. It was for a dual channel 20 MHz CRO. I bought it 20 years ago.

I would’ve been extremely happy getting it. I was only in year 11 back then. I don’t know how I convinced my dad to pay $799 for it, must have been a lot of money back then.

CRO Receipt

I bought the oscilloscope from David Reid Electronics, one of the three electronics shop that was on York St, Sydney. I like that shop, it’s sad to see that shop closed down.

Fluke 17B Multimeter Mini Review

I just got my Fluke 17B multimeter yesterday. I bought it from DealExtreme for USD $92 delivered. I’d like to use this multimeter instead of my Fluke 77 III for my everyday electronics at home.

This Fluke model is only for sale in China, however you can easily get this model from Ebay or DealExtreme. Given that it is only for sale in China, there aren’t many in depth review of it. My concern is that this model may not be of the same quality as the other Fluke’s model.

This meter has a sister model, the Fluke 15B which does not measure frequency nor temperature.

For more information, calibration manual of the meter is avaliable from Fluke China website here.
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Go Hexi!!

Meet Hexi. Hexi is my new 6-legged robot (hexapod) family member. He is demonstrating the three standard walking pattern for a hexapod: wave, tripod and ripple gait. For now he can only walk in a straight line.

Body: Lynxmotion Phoenix
Actuator: Hitec HS-645MG servos
Processor: ARM Cortex-M3
Battery: 5 Sub-C 5000 mAh (

Hitec Servo

These are some of Hitec servos that I looked at:

Size Speed

(Time/60° (s))

Torque ( Price


Bang per buck (Torque/Time/Price)
HS-475HB Standard 0.23 4.4 15 1.3
HS-645MG Standard 0.24 7.7 34 0.9
HS-985MG Standard 0.16 9.6 58 1.0
HS-755HB 1/4 0.28 11.0 25 1.6
HS-805BB Mega 1/4 0.19 19.8 34 3.1


Micro 0.17 3.6 41 0.5


Standard 0.23 10.3 48 0.9

For standard size analog servo, the HS-985MG performs best. It is based on a coreless motor. It provides the highest torque as well as the fastest speed.

The HS-475HB is the best value servo. It has the advantage of using Karbonite (just like kryptonite 🙂 ) gears. Karbonite is supposed to be stronger than nylon but has less wear and tear compared to metal.

The HS-645MG has good torque compromise without being overly expensive. It uses mostly metal gear.

For a mega 1/4 scale servo. The HS-805BB looks awesome.