Least component LED flasher - Page 1
Forum section: electronics / beginners

author: kalel
author_rank: Frequent Contributor
timestamp: November 15, 2017, 01:56:17 pm
content: Some of you might blame me for posting this question at all, but I'm curious about simple oscillator circuits that can flash an LED (not a self flashing one).Doing a simple web search definitely returns a lot of LED flasher circuits, and searching for the "simplest" types usually finds circuits using the oscillation of a self-flashing LED or sometimes the ~12v reverse bias single transistor circuit (I have tried that one already, and it did work with my transistor at some voltage).There is no specific goal, just curiosity, but here is what I'm looking for, ordered by importance (high to low):- The smallest amount of components used (ICs allowed)- Should work with reasonable voltages (e.g. 5v) and it doesn't need high current, 1 LED is enough- Any waveform that works, duty cycle does not need to be adjustable- Frequency adjustable ("flashing rate") with a potentiometer, no specific frequency required, as long as it is visible (one end of the pot might even go out of visible blinking range)I know about some 555 timer, dual transistor circuits that are relatively simple and work, but there might be some circuits with even less components needed.Recently I learned about "http://solarbotics.net/library/datasheets/LM3909.pdf" which is very simple, but the "variable flasher" example does add a few components.

author: mariush
author_rank: Super Contributor
timestamp: November 15, 2017, 02:14:28 pm
content: The simplest these days would probably be a 6-8 pin microcontroller with ADC (for the potentiometer, unless going with some other adjust mechanism like two up/down buttons ) and internal oscillator or RC or some other way to generate a clock internally. One part and it's as low as 20-30 cents in volume.Otherwise, you should look into the Flashing Light contest where you get the weirdest / wackiest ways to blink a light including relays, solenoids, all kinds of tricks to make incandescent light turn on and off.Here's the link :https://www.flashinglightprize.com/Example of microcontroller ..attiny10 :https://www.digikey.com/product-detail/en/microchip-technology/ATTINY10-TSHR/ATTINY10-TSHRCT-ND/2136158Speed 12MHzConnectivity -Peripherals POR, PWM, WDTNumber of I/O 4Program Memory Size 1KB (512 x 16)Program Memory Type FLASHEEPROM Size -RAM Size 32 x 8Voltage - Supply (Vcc/Vdd) 1.8 V ~ 5.5 VData Converters A/D 4x8bOscillator Type InternalOperating Temperature -40°C ~ 85°C (TA)Package / Case SOT-23-6PIC10F320Thttps://www.digikey.com/product-detail/en/microchip-technology/PIC10F320T-I-OT/PIC10F320T-I-OTCT-ND/2772076Core Size 8-BitSpeed 16MHzConnectivity -Peripherals Brown-out Detect/Reset, POR, PWM, WDTNumber of I/O 3Program Memory Size 448B (256 x 14)Program Memory Type FLASHEEPROM Size -RAM Size 64 x 8Voltage - Supply (Vcc/Vdd) 2.3 V ~ 5.5 VData Converters A/D 3x8bOscillator Type InternalOperating Temperature -40°C ~ 85°C (TA)Package / Case SOT-23-6

author: Howardlong
author_rank: Super Contributor
timestamp: November 15, 2017, 02:36:18 pm
content: Microcomtroller as mentioned the very least componenent count if you forego niceties like decoupling caps and voltage regulators.Schmitt trigger?One IC, one cap and one pot.

author: bd139
author_rank: Super Contributor
timestamp: November 15, 2017, 02:39:10 pm
content: M34 LED flasher IC:http://www.bowin-ic.com.hk/IC/Export%20Items/M34.pdfNeeds supply, itself and LED. No series resistor required or any other components. Works down to 3v.Or the ubiquitous LM3909 if you want more features:http://solarbotics.net/library/datasheets/LM3909.pdf

author: james_s
author_rank: Super Contributor
timestamp: November 15, 2017, 08:32:51 pm
content: Not sure I'd call the LM3909 ubiquitous. IIRC it was discontinued years ago and never achieved widespread use outside of the hobbyist community. I never saw one in any commercial product although it must have been used. Usually a simple transistor circuit was cheaper and worked well enough.

author: capt bullshot
author_rank: Super Contributor
timestamp: November 16, 2017, 12:58:41 pm
content: Simplest circuit: connect a self-flashing light bulb (yes, these with bi-metal switch inside) in series to the LED. Flashing frequency will be a bit at random, you could vary it a little by putting a beefy pot in series

author: capt bullshot
author_rank: Super Contributor
timestamp: November 16, 2017, 01:03:07 pm
content: Next simple solution: a relaxation oscillator using a neon bulbSomewhat more electronic: replace neon bulb by a small signal thyristor or a PUT (programmable unijunction transistor)I've build a 25-fold LED flasher based on PUTs in my youth:http://wunderkis.de/Blinkenlights/blinkedinger.htmlScroll down until "Das Mega-Schieberegister mit Blitzdings", look for the 5x5 square arrangement of yellow LEDs.

author: soubitos
author_rank: Frequent Contributor
timestamp: November 16, 2017, 01:17:35 pm
content: I think the basic Joule Thief circuit is the possible winner with oscillation frequency in the range of several 10s KHz....I have seen some added caps forcing the oscillation freq. lower so it becomes visible but havent tried any of them and dont have any use for such a circuit either

author: kalel
author_rank: Frequent Contributor
timestamp: November 16, 2017, 01:31:14 pm
content: Quote from: soubitos on November 16, 2017, 01:17:35 pmThanks, for this purpose the basic circuit frequency is too high, but it's good to know that it can be adapted.

author: NivagSwerdna
author_rank: Super Contributor
timestamp: November 16, 2017, 01:38:17 pm
content: I'm thinking about working on a project that goes to the other extreme... usinghttp://www.ti.com/product/LP5569LP5569 is quite a fun chip (and it's VERY small) that allows you to program a flash sequence.... but it is volatile so you need a MCU to load it via I2C.re: OP...http://uk.farnell.com/kingbright/l-56bhd/led-blinking-5mm-bright-red/dp/1142543

author: Zero999
author_rank: Super Contributor
timestamp: November 16, 2017, 01:58:04 pm
content: The cheapest LED flasher is a Schmitt trigger oscillator, made with the 74HC1G14. The circuit is on page 10, figure 16, of the data sheet.https://assets.nexperia.com/documents/data-sheet/74HC_HCT1G14.pdf