That push button bistable I have still yet to get going is part of an attempt to replace an led in an existing lamp with a choice of two.
I thought I would reveal the rest of my circuit for scrutiny.
The idea is that the whole circuit connects directly into the lamp instead of the existing led, stealing a few microamps to run itself.
The pairs of diodes ensure that there is always a load on the power source, which is a dc-dc converter, even during switching.
I tried just one diode, but the Cree leds I am using seem quite happy to produce a significant amount of light, even with only 2.5V across them.
The two diodes cut this to about 2.2V when the active led is dropping 3V, leaving only a faint glow from the nominally 'off' one.
'Alice'
Respond below, or to alice@electronicsweekly.
No email addresses are collected for marketing purposes from responses to this blog.
I will keep it that way for as long as possible.
Comments (4)
How do I post a picture in a comment ? I have a nifty little circuit as an alternative to the 74HC74
Posted by Mike Meakin | February 1, 2010 2:34 PM
Posted on February 1, 2010 14:34
Sorry, what ever we try, the comments on Movable Type seem to be picture-proof.
I am most interested in this - I once made one with NOR gates in a ring but, although it worked, I was never quite sure how.
You can email it to alice@electroncsweekly.com and I can stick it up in a new posting, or add it to this one.
'Alice'
Posted by 'Alice' | February 1, 2010 4:45 PM
Posted on February 1, 2010 16:45
Will not a switch alone suffice?
2 LEDS, to 2 poles of a toggle switch.
Position 1 connect LED 1, position 2 the other LED.
Posted by Stuart | February 11, 2010 12:06 PM
Posted on February 11, 2010 12:06
Thanks Stuart.
I did think about a toggle switch, what stopped me was that there was only a tiny place to mount the switch, and it had to be glove-friendly.
As well as that, the control had to be at the end of some wires and I worried about RFI because the supply to the leds is noisy.
'Alice'
Posted by 'Alice' | March 22, 2010 4:56 PM
Posted on March 22, 2010 16:56