LEAP#209 a funky little LED display
I found this interesting LED display at Sim Lim Tower, and grabbed one to test. The LED unit combines 7 x 7-segment display (no decimal points) and 7 indicator LEDs (Red-Green-Yellow).
It is marked as "72R02PHIL T9717". I have no idea what that means(!), and of course there's no sign of a datasheet on the net, so pinouts needed a bit of reverse-engineering. All in all, an interesting display unit for a combination of numerical and status display.
As always, all notes, schematics and code are in the Little Electronics & Arduino Projects repo on GitHub.
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LEAP#208 Single Stage FM Transmitter
I've been experimenting with FM, and the hardest thing to get right tends to be the hand-wound coils. So to get a baseline, I picked up a 1-transistor kit during a recent visit to Sim Lim Tower.
As always, all notes, schematics and code are in the Little Electronics & Arduino Projects repo on GitHub.
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LEAP#207 Frequency Counter
Testing a CMOS frequency counter circuit with a 100Hz - 5MHz range.
I found this circuit published in Electronics magazine (Sep 16 1976). It's a classic demonstration of the CD4026 "bucket-brigade" and CD4047 astable oscillator.
The frequency counter is governed by a CD4047 oscillator. Since this offers a clean 50% duty cycle, it is ideal for flipping the circuit between two modes: sampling period; display period.
As always, all notes, schematics and code are in the Little Electronics & Arduino Projects repo on GitHub.
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LEAP#206 CD4047 Astable Oscillator
The CD4047 is capable of running in astable or monostable configurations, with operating frequency configured by an external RC network. So in one sense, sounds like the 555 timer!
Unlike the 555, the CD4047 provides a fixed 50% duty cycle with good frequency stability (+/- 2% @ 100KHz).
As always, all notes, schematics and code are in the Little Electronics & Arduino Projects repo on GitHub.
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