Blinking LED on 1.2V - Internet Box from The IT Crowd tv series - Page 1
Forum section: electronics / beginners

author: dhlavaty
author_rank: Newbie
timestamp: July 29, 2014, 12:44:43 pm
content: I know, I know. There are tons of LED blinkers out there on the internet. I have spend weeks searching for them already, but still doesn't found one matching my criteria.I want to build simple "Internet box" ( seeThe IT Crowd - Series 3 - Episode 4: The Internet)But to learn something useful (some low-voltage stuff) for me, I want to drive it from one single 1.2~1.5 Volt battery (so I can use any AA / AAA NiHM accumulator and/or classic AA / AAA / C / D 1.5V battery). And of course, the longer battery life, the better. Red 1.8~2.3V LED will be absolutely fine, but some more universal scheme with blue 3.2V LED will be appreciated.1.I have found several designs, that just flash (LED is on for about 4ms with one flash per second), but I want do make something like 1 Hz ~ 1 second on / 1 second off. Accuracy is not important.2.I also found some schemes using LM3909 Oscillator IC, but that chip is not manufactured anymore.3.Then I found some M34 LED Flasher Chip, but I cannot found any supplier for it and the minimal voltage is 1.35V.4.Someone suggested an LT1073 DC-DC Converter, but what then ? Use an 555 timer ? Low-power micro-controller ? Which one ? Is there any possibility, that it will blink for at least a month from one AA / C or D type battery ?Thanx for any advise.

author: Wh1sper
author_rank: Regular Contributor
timestamp: July 29, 2014, 12:51:36 pm
content: PR 4404Low Voltage Boost Driver for 0,5 / 1,0 W Power-LEDsThe PR4404 is a step-up converter for white LEDs, operating with single battery cellsupply (1.2/1.5V) at up to 150mA LED current or dual cell supply (2.4/3.0V) at up to300mA LED current. A minimum part count allows compact and cost-efficient solutions.The converter can be switched on and off with a logic signal, which is useful e.g. for PWMcontrol, timer circuits etc.Works down to 1.00Volts

author: rob77
author_rank: Super Contributor
timestamp: July 29, 2014, 01:49:06 pm
content: what about using 2 cells and building a simple LED blinking circuit (simple astable multivibrator, or 555...or whatever)the "internet box" is big enough to place even more that 2 cells. i would rather spend 50cents more on the battery holder to get the double cell one and another 50cents for the extra AA batery , than building a complex electronics worth of 15$ to blink a LED

author: dhlavaty
author_rank: Newbie
timestamp: July 29, 2014, 02:04:45 pm
content: @Wh1sper: Thanks for suggesting PR4404, but as I mentioned in my first question - what next ? 555 ? Micro-controller ? Which one ?@rob77: As I mention in my question, purpose (at least for me) is to learn something useful (low-voltage stuff). So my own goal is to use 1.2V battery and "blink with it" as long as possible.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: July 29, 2014, 02:14:36 pm
content: Microchip MCP1640

author: mariush
author_rank: Super Contributor
timestamp: July 29, 2014, 02:20:42 pm
content: You can use some plain diodes and capacitors to do a voltage multiplier, raising the voltage to 3v or 5v:http://www.allaboutcircuits.com/vol_3/chpt_3/8.htmlVoltage multipliers work for a few mA, enough to power a led and potentially a 6-8 pin mcu to blink the led (or just get a led with blink functionality built in). Note that it won't scale for more than a few mA, you'll need a boost regulator to do that.ps. shit, forgot about dc... voltage multipliers work with ac, not dc voltage. yeah, boost regulators... search digikey or farnell/newark/mouser for one that works from 1-1.2v and you're golden.

author: Mr Smiley
author_rank: Frequent Contributor
timestamp: July 29, 2014, 04:18:27 pm
content: The LM3909 was sold in the millionsIt was used for flashing the led on the edge of the cardboard outer sleeve case of the Pink floyd CD album 'Pulse'Mine lasted a good few years before the original battery finally retired O0 and it's still flashing today ( with battery changes since the day i bought it)

author: Zero999
author_rank: Super Contributor
timestamp: July 29, 2014, 08:06:31 pm
content: A Joule Thief circuit with a flashing LED?You'll probably need to make a few modifications but it should work.A low voltage CMOS Schmitt trigger inverter oscillator and a voltage doubler made with a Schottky diode.Or build a discrete LM3909.http://home.cogeco.ca/~rpaisley4/LM3909.html

author: dhlavaty
author_rank: Newbie
timestamp: July 30, 2014, 07:02:42 am
content: @mikeselectricstuff> Thanks. MCP1640 looks great. And (as always, my question): What then ? 555 ? microcontroller ? Which one ?@MrSmiley> I have mentioned LM3909 in my first question, but it is not manufactured anymore. And once again, I want to learn something useful and not something outdated ;-)@Hero999> I have seen some Joule thief schemes, but all of them just flash with a diode (so LED was on for just about 4miliseconds). Own discrete LM3909 may be a nice solution. Thanx

author: Mr Smiley
author_rank: Frequent Contributor
timestamp: July 30, 2014, 10:36:06 pm
content: unijunctionhttps://www.inkling.com/read/make-electronics-charles-platt-1st/chapter-2/experiment-11

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: July 30, 2014, 10:39:42 pm
content: Quote from: dhlavaty on July 30, 2014, 07:02:42 amMaybeQuoteAny, absolutely any microcontrollerA flashing LED would be the simplest

author: hlokk
author_rank: Contributor
timestamp: July 31, 2014, 05:04:30 am
content: If you wanna learn and go a dozen components then the above should give you a start.But if you just want results for cheap and easy, then go a flashing led (blue even, e.g.http://www.ledsales.com.au/shop/index.php?main_page=product_info&cPath=148_152_154_155&products_id=461) and then grab one of these IC's and an inductor (http://www.ledsales.com.au/shop/index.php?main_page=product_info&cPath=131_132&products_id=384).Wont be able to control the flash rate though. Using 2-3 batteries will mean you can just use a flashing LED and a resistor which you can get anywhere.

author: IanB
author_rank: Super Contributor
timestamp: July 31, 2014, 05:14:35 am
content: A joule thief circuit feeding a reservoir capacitor through a diode should give a DC voltage of about 5 V or so. You could then use this to run a 555 timer circuit with the mark/space ratio of your choice and blink the LED with that.

author: dhlavaty
author_rank: Newbie
timestamp: July 31, 2014, 07:55:40 am
content: @MrSmiley > That 2N6027 programmable unijunction transistor look interesting. I will definettly look at that. Thanx.@mikeselectricstuff > MCP1640's are nowhere in stock (at least not here in EU or with a normal postage). But I have found MAX756/MAX757, do you know it ? Is it simmiliar ? And what do you think will last longer on one battery, 555 or a low power micro ?@hlokk > Yes I know some blinking LEDs. thanx@IanB > Yes I was considering 555, but I'm not sure about power consumption. thanx

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: July 31, 2014, 09:23:02 am
content: Quote from: dhlavaty on July 31, 2014, 07:55:40 amLow power micro, using the watchdog timer, but a CMOS 555 (7555) would be a big improvement over the standard one.Another low-power simple option is a CMOS 4060 oscillator/counter