Category Archives: Electronics

Design and Construction of a 24 GHz Low Noise Amplifier

24GHz Low Noise Amplifier

 

Tony Long and I designed and built a 24 GHz low noise amplifier for our ECE192 undergraduate independent study project at UCSD.

The amplifier was designed with an early version of Agilent ADS, PCBs were fabricated on Rogers 5880 (Duroid), and we hand built several prototypes on K-connector fixtures that Tony designed. Measured results were consistent with our simulations.

Closeup of two stage LNA PCB

Tony and I won an award for this project at the Eureka! undergraduate research conference in June 2000.

I heard recently that this project is being used as an example of a good EE senior design project at other universities, so I dug up an original copy of the paper we submitted and posted a PDF here.

Hexbright Hacking

The Hexbright is an Arduino-compatible open source flashlight that was the subject of a very successful kickstarter campaign in 2011.

Today I spent a short time working on some custom firmware for it.

My firmware adds two new features:

  • Button presses cycle between modes (low, med, high brightness) as usual, but if you wait longer than CYCLE_DELAY (default 5 seconds) between presses, the next press turns the hexbright off.
  • If the hexbright is left on for longer than AUTO_OFF_MINUTES (defaults to an hour), the hexbright turns off.  Handy for when you prop the light somewhere and forget about it.

You can download my custom Hexbright Arduino sketch here.  If you’re new to the Hexbright, read these well-written instructions first.  You’ll need to install the required USB driver and Arduino board configuration file.

Amazon link: HexBright FLEX, 500 Lumen Programmable LED Flashlight

HSC Santa Rosa closing on May 4th, Closeout Sale starts April 27

HSC Santa Rosa (actually Rohnert Park) is closing their doors on May 4th. They are having a closeout sale that begins next weekend (April 27th) and runs through the 1st week of May.

I visited this small but convenient Halted branch often while I worked in Santa Rosa, and I’m sad to hear this news. Fortunately, I’ll be in the area next week and will have one last chance to visit before the store closes. (Unfortunately, I’m traveling by air, so I won’t be able to bring too much surplus junk back home.)

HSC closed their Sacramento store in 2007. With Rohnert Park closing next month, the original Santa Clara location will be the only one remaining.

More details below.

Special Announcement

Attention HSC Customers:

After 27 years in the Santa Rosa area, HSC Electronic Supply of Rohnert Park is closing its doors for good on May 4, 2013. Halted Specialties Co. Inc. will continue to operate its main store, HSC Electronic Supply of Santa Clara.

Store Closing Sale!

Rohnert Park Location Only.

Storewide Liquidation!

20% to 80% Off Entire Stock.

Saturday, April 27th to Saturday, May 4th

Our shelves are spilling over in Santa Clara so we’d rather blow it out than truck it back to support on-going Santa Clara operations. Please stop by to check out this last opportunity for deals in Rohnert Park and stop by our Santa Clara store when visiting Silicon Valley. Don’t forget to visit us at www.halted.com as well.

Thank You,

HSC Management

via South County ACS

Bus Pirate v4 oscillates too. Tantalum cap to the rescue!

This week I finally received my Bus Pirate v4 from Seeed Studio.

The first thing I did after opening the box was to probe the 3.3V rail with the BP internal power supply enabled.

Here’s what I saw:

Bus Pirate v4 3.3V rail oscillation

That looks familiar!  Except this time it’s an oscillation at 5.9kHz and 400mVpp!  (almost 4 times what I saw on the SFE Bus Pirate).

I replaced C11 with a 4.7uF tantalum surface mount cap that I scavenged from another board, and the oscillation went away completely:

Bus Pirate v4 - C11 = 4.7uF tant

 

Ahh, that’s better!

Again, I strongly suspect the low ESR of the ceramic cap is to blame.  The 3.3V regulator really needs to see the higher ESR of a tantalum or electrolytic cap for stability.

My advice to all Bus Pirate owners is to check your 3.3V rail with a scope, if possible, and replace C11 with a tantalum or electrolytic cap.  Alternatively you may be able to add a small amount of resistance in series with the ceramic cap that comes with the Bus Pirate, but I haven’t verified this.