Anyone know of such a thing - self contained to run off 12 volts? Can get ones with a 50% duty cycle, but was looking for more like 1 flash per 10 seconds to cut down current consumption. And no room inside enclosure for more than a standard 5mm LED.
Take a look at Maplins... Failing that, look at using a CMOS version of a 555 timer IC with an LED. The later would enable you to set some very long intervals between flashes.
Problem is there's no space for anything other than the LED. And since you get self contained flashing LEDs - but with a 50% duty cycle - I was hoping there was something similar for my needs.
Didn't realise they'd been discontinued (wonder why?). I bought a tube of them ages ago, which lasted a good long while. I'll buy some up next time I come across them.
I'm guessing it was just lack of demand. I suppose there's only so many 'low-current-flashing-LED-and-nothing-else' applications you can think of before the novelty starts to wear off!
be worth a look. I believe you are familiar with diddling with electronics, so you should be able to adapt the guts of one of those devices, should you need. You should look through Land Rover International, they used to have advertisement for a decoy security alarm which used to blink a LED every so often. Incidentally on my bicycle I have a LED rear light in conjunction with dynamo lighting. My inquisitiveness knowing few bounds, I hooked it up to a "sillyscope" and found that it was actually a square wave with a 1:4 ratio, fast enough for persistence of vision, but cunningly saving battery life. These new clip-on ones are useful for hillwalking, if you get into trouble (and I have considerable experience and because of this I am not complacent, it CAN happen) it will make you very prominent in the dark.
The duty cycle and therefore current consumption is too high. I'm looking for perhaps one flash every 10 seconds, but bright enough to be seen in daylight.
Back in the very early days (maybe 1990-92) of flashing LED's someone (maybe HP?) made one with 3 terminals that used an external capacitor to adjust the duty cycle, I think it had a forward voltage of around
7v so would still have needed a dropper resistor to run on 12v.
It's part of the intruder sensor on a car alarm. Originally, it had a dim LED which didn't flash and you couldn't see in daylight. I replaced it with a bright flashing one, but there's no room for extra electronics - like a 555 - inside the case as there's already a PCB for the intruder sensor. I could re-wire it using multicore cable and site a timer elsewhere, but was looking for the easy option.
I'm trying to cut the quiescent current on a car sometimes not run for two weeks or more. At the moment it's over 150mA due to radio, alarm/immobiliser and central locking unit, etc.
You don't want a 555 anyway. They draw a ridiculous amount of current.
Get a battery conditioner? Or if the car isn't near the mains, use a motorsport battery switch to disconnect everything except the alarm? (More security, too.)
(My Cossie would flatten its battery completely in less than 2 weeks...)
I have had a good look around, and mostly they are kits, with wired components, I am sure you can create what you want out of the bits with a few changes. Ready made seems not to be an option.
The CMOS one is fine. 7555 I've used this on the new central locking controller and got the quiescent down to .018mA. ;-) From 35mA. Mr Lucas wasn't to clever with circuit design in the '70s.
Car parked in the road.
Could do, but then the radio and OBC would loose their mememory - and I'd have no remote locking.
Yes. I'm being a tad genererous and assuming a fully charged battery.
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