Thursday, August 25, 2022

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Mailbag #20

A nice mix of bits and pieces arriving this week, including some photodiodes and some really interesting SMD inductors.

The big finish is a pile of 5V LED cobs - could come in very handy for lighting the bench and eliminating all shadows.

Here is the video for your enjoyment!



Friday, August 19, 2022

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"SuperCap" Solar Candle

The attiny13 based solar candle has been a success - based on a "joule thief" modified circuit that runs a micro-controller to ramp a couple of LEDs up and down to simulate a night time candle.


The attiny13 runs at 128kHz, the code is written in assembly to minimise overhead and the hardware is optimised to reduce power requirements.

Then along comes a couple of weird ideas out of left field!

1. Use the Padauk PFS154 or the PMS150C microcontrollers, both of which have an extra PWM channel to give three ramping channels of candley goodness vs two (for more authentic fakery).

2. Run the Padauks at 53kHz to further reduce power.

3. Craziest - replace reliable affordable NiMH rechargeable batteries with unknown super capacitors! Huh?

Stage One and Three are done, but even with 30F supercaps I'm not currently get more than a few hours of candle imitation. I've yet to deploy the 5050 LEDs which I normally use to reduce power - so there's a possible saving.

I have also yet to spend any quality time cranking the Padauk's clock to ILRC AND successfully maintaining good PWM.

I believe that I am chasing a foolish dream at this stage - but I want to eliminate all possible barriers to the concept of a candle that in 2500 years time (based on 1 million charge/discharge cycles) is still providing a reassuring lovely glow in the wee hours.





Friday, August 12, 2022

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Mailbag #19

Great piles of "useless wire critters"™ coming in to the Southern Climes.

Enjoy this mailbag - I did, especially the enigmatic "forbidden tech". That should be fun to get blinking one day.

™ registered Trademark belonging to the Minister of Finance in this house

 

Saturday, August 6, 2022

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CD40106 Hex Schmitt Inverter IC

One of my processes for choosing a topic or theme for this blog and video is to look into the "buckets of wire critters" and randomly choose an IC, then research for a bit about how it might be usefully employed.

And so it came to pass that I spied a few CD40106 ICs which I had ordered in June of 2018 (and then forgotten).

The CD40106 is a hex Schmitt-Trigger inverter which has a score of useful circuits with it at the heart. For instance in the datasheet we see applications including wave and pulse shapers, high-noise-environment systems, monostable multivibrators and astable multivibrators.

Here is the pinout:

However, in the course of researching I found a "train crossing" circuit which used three 555 chips to simulate a warning and then actual flashing LEDs.

I was surprised that this 555 based circuit came up as a "hit" when I was searching for CD40106 - but when checking the bottom of the website I found the following circuit.

Whilst the circuit is fairly simple to both understand and construct, I was stymied by the first lot of ICs I picked up being clearly faulty.

Firstly, they did not behave as expected (blinking at odd times although not as per the circuit). The biggest problem was that after a few minutes they went into a short circuit, thus triggering the current limiter on my power supply, and refusing to do any more work!

Fortunately the second batch I tried worked and worked well.

I'm thinking that although this was a "train crossing" application it would suit an "alarm" style circuit - perhaps even with a "cancel" option as per a commercial home alarm.