rspangle@jarthur.Claremont.EDU (Randy Spangler) (06/28/90)
I recently was looking for bright LED's to stick on my rollerskates, and the only really bright ones I could find were red. This got me wondering what the brightest standard-size one element LED's of various colors are. There's also gotta be some physical reason why red ones are easiest to make brightest. The red ones I got were from Radio Schmack, and put out 2000 mcd. Also, what's the easiest way to blink a high-current LED at say 2-10 Hz? I've heard there's some way to do it with a 555 timer, but electronics isn't my strong point. Blinking LED's (that have the driver built in) seem to be a lot dimmer than non-blinking ones. -- -------------------------------------------------------------------------- | Randy Spangler | The less things change, the | | rspangle@jarthur.claremont.edu | more they remain the same | --------------------------------------------------------------------------
maddog@athena.mit.edu (Matthew J Marjanovic) (06/29/90)
In article <7644@jarthur.Claremont.EDU>, rspangle@jarthur.Claremont.EDU (Randy Spangler) writes: |> |> Also, what's the easiest way to blink a high-current LED at say 2-10 Hz? |> I've heard there's some way to do it with a 555 timer, but electronics isn't |> my strong point. Blinking LED's (that have the driver built in) seem to be |> a lot dimmer than non-blinking ones. |> If you want blinking LED's pretty easy, try the LM3909 (if I remember the number correctly) LED Flasher chip, designed for just that purpose. You can find the chip anywhere that sells the standard stock of linear IC's (such as Jameco, Digi-key, etc. Radio Shack may even carry it.). The data sheet for the chip lists a couple of pages of applications, most of which will pulse a LED for years off of a single 1.5 volt battery with one or two capacitors (values provided). Most of the schemes have a higher current / lower duty cycle, which give bright pulses. It couldn't be any easier (except for the blinking LED's themselves.) |> |> -- |> -------------------------------------------------------------------------- |> | Randy Spangler | The less things change, the | |> | rspangle@jarthur.claremont.edu | more they remain the same | |> -------------------------------------------------------------------------- ____________________________________________________________________ Matt Marjanovic | "He who has never envied the vegetable, maddog@athena.mit.edu | has missed the human drama." | -- E.M. Cioran --------------------------------------------------------------------
whos@ddsw1.MCS.COM (Ben Feen) (06/30/90)
In article <7644@jarthur.Claremont.EDU> rspangle@jarthur.Claremont.EDU (Randy Spangler) writes: > >I recently was looking for bright LED's to stick on my rollerskates, and the >only really bright ones I could find were red. This got me wondering what ... >Also, what's the easiest way to blink a high-current LED at say 2-10 Hz? >I've heard there's some way to do it with a 555 timer, but electronics isn't >my strong point. Blinking LED's (that have the driver built in) seem to be >a lot dimmer than non-blinking ones. An RC circuit should do it: + Resistor LED ------------------- \ | | / --- \v/ \ --- --- - / | | ------------------- Capacitor To calculate frequency - Ohms*farads = 1 time constant (In seconds) Multiply TC by 5 to find frequency. More I can't remember, but others should be able to build on this. -- whos@ddsw1.MCS.COM | I don't know, who's at DDSW1? | whos@ddsw1.MCS.COM! I asked YOU who's at DDSW1! Ok, there's a guy at DDSW1, right? | Right! Who? | Exactly! | What? | No, he's at lll-winken. | Where? | No, What! | I don't know! | He's at gargoyle. | Who? | No, he's at DDSW1.MCS.COM!
olbers@bobcat.ent.ohiou.edu (Robert Olbers ece) (07/04/90)
In article <1990Jun29.215920.4003@ddsw1.MCS.COM> whos@ddsw1.MCS.COM (Ben Feen) writes: >In article <7644@jarthur.Claremont.EDU> rspangle@jarthur.Claremont.EDU (Randy Spangler) writes: >> >... >>Also, what's the easiest way to blink a high-current LED at say 2-10 Hz? >>I've heard there's some way to do it with a 555 timer, but electronics isn't >>my strong point. Blinking LED's (that have the driver built in) seem to be >>a lot dimmer than non-blinking ones. >An RC circuit should do it: > >+ Resistor LED >------------------- > \ | | > / --- \v/ > \ --- --- >- / | | >------------------- > Capacitor > > >To calculate frequency - >Ohms*farads = 1 time constant (In seconds) >Multiply TC by 5 to find frequency. More I can't remember, but others should >be able to build on this. > This circuit won't blink the LED from a dc source. The LED needs a current-limiting resistor in series to prevent burnout, and the capacitor will simply charge to the supply voltage and stay there. The simplest way to blink an LED (for those who are not electronically inclined) would probably be the LM3909 IC which is specially designed for this purpose. These are even available at Radio Shack. Here is an example of a 555 LED-flasher circuit: (+) --------------------------------------------------------- | | | | | | / --- | | | \ R1 --- 0.1uF | | | / NC | | | NC | \ ----- | ------- | / ------- | ----| | | | | \ | -------------------------- | | / R3 | | 8 7 6 5 | | | \ / | | | | | R2 \ | 555 | | | | / | | | | --- \ | 1 2 3 4 | | | \ / | -------------------------- | | v LED | | | | | |NC | --- ------- | ----| | ------------------ | NC | | |NC | | | |---- | ------------ | | | | | | --- ------------------------------------ | --- | | C (-) -------------- (Excuse the 'professional quality' schematic 8) ) NC = no connection The LED will be on* for time T1 = 0.693 * ( R1 + R2 ) * C and will be off* for time T2 = 0.693 * R1 * C *(I may have the 'on' and 'off' reversed) R3 is used to set the LED current; e.g., assuming 9V input, 20 mA desired on-state LED current, and an LED voltage of 1.7 V (red LED), R3 = ( 9 - 1.7 ) / 0.02 = 365 ohms For high levels of current, the 555 may need to drive the LED(s) through a transistor -- check the 555 specs. R. L. Olbers Ohio University ECE Department
ardai@teda.UUCP (Mike Ardai) (07/05/90)
The 0.1 uF cap on pin 5 should go to ground (-), not Vcc (+). According to the spec sheets, it can source or sink 200 mA, so a transistor should not be needed. /mike -- \|/ Michael L. Ardai Teradyne EDA East --- ------------------------------------------------------------------------- /|\ ...!sun!teda!ardai (preferred) or ardai@bu-pub.bu.edu
pianin@bbn.com (Jerrold Pianin) (07/07/90)
In article <7644@jarthur.Claremont.EDU> rspangle@jarthur.Claremont.EDU (Randy Spangler) writes: > >Also, what's the easiest way to blink a high-current LED at say 2-10 Hz? >I've heard there's some way to do it with a 555 timer, but electronics isn't >my strong point. Blinking LED's (that have the driver built in) seem to be >a lot dimmer than non-blinking ones. > Try putting a blinking LED in series with the high-current one.