I copied n pasted from a larger schematic.
I thought I took that out??
for one LED all you ned is a 2n2222
sorry for the booboo
you still need to add a resistor to led depending on voltage.
see audiogurus post
you don't need the tip 120
I copied n pasted from a larger schematic.
I thought I took that out??
for one LED all you ned is a 2n2222
sorry for the booboo
you still need to add a resistor to led depending on voltage.
see audiogurus post
look at my LT spice post
reconfiguring so LED turns on slower
Don't make MrDEB's defective circuit:Originally Posted by smudgepost
The timing resistors are backwards so it will ramp on the LED fairly slowly then will try to switch off for such a small amount of time that the LED will appear to be on continuously.
But since there is no current-limiting the LED will burn out.
Uncle $crooge
This thread has grown and I'm really pleased. I want to try building them all! I am stuck on time for version 1.0 of this so will likely stick with 555 but if the newer 7555 idea works better then I might just use that. The keypad interface is very interesting and will read more tomorrow. I will likely run with the double 555 circuit initially and use a 2n2222 as suggested mainly as these are the parts I've got. If you could help me understand what I need to do to fix it before I burn it that would be great.
As a recap, I'm limited on space so opted to use button batteries so could probably squeeze upto 6V inside. That' my only bottle neck in the planning. I also bought a 5mm and 3m super bright white LED for the flash and am plan to use a piezo for the sound. Oh and yes I would prefer a steady blink to a bold on/off flash.. if possible.
Hardware - easy, know-how - not so easy..I know some traditional people are against always reverting to a microcontroller, but it would be perfect for this situation.
- you can get your timing perfect for the on/off ratio.
- it can perform you fade in fade out function with a pwm
- some run off 3v
- 8 pin SMD chips are tiny
- they can sink/source up to 25mA which is enough to drive an led.
- minimal parts required, led, microntroller, 1 or 2 caps,battery, and a switch for function select.
Of course the downsides are you need the programming knowledge and hardware
Last edited by smudgepost; 8th October 2009 at 12:31 AM.
Button batteries have such a low capacity that the LED will turn on for only a few times. You must blink an LED fairly dimmly and for very short durations for some button cells to last for a few hours.
Button batteries power items with an LCD display that does not produce light so its current is very low.
Uncle $crooge
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