I'd probably try playing with an old cmos 4060 (and I forget the part number of the other one), has an oscillator and should find suitable outputs from the dividers D On 1 April 2017 at 20:30, CDB wrote: > I was chatting with someone from work the other day and the conversation > turned to them wanting to put an LED on their quadcopter which had a > strobing light similar to the navigation light on an aircraft, the one > that appears to make quick succession flashes that increase in frequency > making it look like one flash-pause pause next flash - pause -flash. > This would be easy to do with three LEDs in parallell, light LED 1 then > LEDs 1 and 2, then LEDs 1,2,3 > > This got me thinking on how to hypothetically come up with a circuit. > > The criteria would be: > > No uP to be used. > Vcc =3D 5V > One white high brightness LED > Flash rate unsure but I suspect around 1 to 2 Hz > As few components as possible > Small footprint. > > Now as I tend to come up with complicated ideas and then work backwards > to simpler ones, I'm looking for comments and other ideas on what I have > thunked up so far. > > 1. The obsolete LM3909 might fit the bill (still available on Ebay) > except I need 3 flashes per period > (https://www.digchip.com/datasheets/parts/datasheet/321/LM3909-pdf.php) > > 2. CD4017/74LS90 decade counter + CD4093/74LS00 NAND gates for > oscillator + 1 74LVC1G27 single triple input OR gate chip connecting the > decade counter outputs to the LED. > > 3. 74LS196 decade counter + CD4046 PLL driven by unijunction > transistor the idea being the frequency will change with the sawtooth > pattern and hence the light pattern will change. > > 4. CD4048 dual retriggable monostable + 555 as oscillator then OR the > two outputs together. > > 5 Pulse generator using an 74LS10 quad NAND gate + 555 as a clock > generator and OR gate at the two pulse outputs driving the LED. > > I've just thought, I suppose I could use a dual 555 timer + driver > transistor. > > I'm sure back in the 80s there were special one chip flasher chips aimed > at toys which did exactly what this circuit needs, but I threw my lovely > paper based Maplins catalogue out years ago (1999 to be precise). > > Comments welcome. > > Colin > > > > -- > > colin@btech-online.co.uk > > Web presence: www.btech-online.co.uk > > Hosted by: www.justhost.com.au > > This email is to be considered private if addressed to a named > individual or Personnel Department, and public if addressed to a blog, > forum or news article. > > > > __________________________________ > Sent from eM Client | www.emclient.com > -- > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .