UBM Tech
UBM Tech

Student requesting EDN design community help

-December 11, 2012

Editor's Note: An embedded systems Masters level student decided to build a simple wireless sensor node. For that he need to build a very simple 433.92MHz transceiver (based on a SAW resonator) which is powered by a 3V coin cell. Any suggestions folks? Your solution will be featured on the home page of EDN and in our Fun Friday newsletter. Here's his problem, in his own words:

As a problem of energy saving, the super-regenerative receiver from EDN Design Ideas in 2006 seems an ideal choice, that is for what I tried to build a receiver using the circuit I found on the web. Really I built just the detector of this circuit (red zone on the schematic attached), and I used an oscilloscope to visualize the output.

The problem I found was at the step of tuning the variable capacitor (I used a variable capacitor instead of a variable inductor), it's difficult to get it stable and when I release it the frequency changes(the capacitance of my hand disturbs the tank circuit) and the sensitivity was poor(just few meters),all this knowing the consumption was average 150uA @3v.

My ultimate goal is to get this receiver working with a sensitivity of 3Om and consumes less than 200uA.

So now I want to know:

1. How to avoid the disturbance of the tank circuit?

2. If I decide to use another HF transistor, how to modify the resistors r5 & r6?

3. How to increase the sensitivity of this circuit to achieve 30m (with minimum energy)?

Click on image to enlarge

I ask the EDN design community to help this young engineer and give him a great lesson in the comraderie that we EE's have worldwide. Please send your comments and advice in the form of comments, schematics, scope shots, etc. on this blog.

Loading comments...

Write a Comment

To comment please Log In