Post by thread:[PICLIST] One transistor LED flasher? [OT]

Am looking for a one transistor LED flasher circuit. Does such an animal exsist? Thank you. John -- http://www.piclist.com hint: To leave the PICList spam_OUTpiclist-unsubscribe-requestTakeThisOuTmitvma.mit.edu>

At 09:40 PM 9/12/00 -0700, John wrote: >Am looking for a one transistor LED flasher circuit. Does such an animal >exsist? Sure. It's called a one-transistor "oscillator". Any book, including Art of Electronics, has designs. What frequency are you interested in? ================================================================ Robert A. LaBudde, PhD, PAS, Dpl. ACAFS e-mail: .....ralKILLspam@spam@lcfltd.com Least Cost Formulations, Ltd. URL: http://lcfltd.com/ 824 Timberlake Drive Tel: 757-467-0954 Virginia Beach, VA 23464-3239 Fax: 757-467-2947 "Vere scire est per causas scire" ================================================================ -- http://www.piclist.com hint: To leave the PICList piclist-unsubscribe-requestKILLspammitvma.mit.edu>

Hi John You can bye flashing LED over the counter. Just add power. The flashing frequency is ~ 1Hz. Thys {Original Message removed}

On Tue, 12 Sep 2000, John Pearson wrote: > Am looking for a one transistor LED flasher circuit. Does such an animal > exsist? You didn't specify what kind of transistor you needed to use, so I'll suggest a unijunction transistor. Good luck finding them though, I don't know if they are still made. Cheers, Bob -- http://www.piclist.com hint: To leave the PICList .....piclist-unsubscribe-requestKILLspam.....mitvma.mit.edu>

UJT relaxation oscillator -- wow its been years! (How about using neon bulb relaxation osc? :-) Bob Ammerman RAm Systems (contract development of high performance, high function, low-level software)s {Original Message removed}

> Am looking for a one transistor LED flasher circuit. Does such an animal > exsist? > well, here is a relaxation oscillator, the frequency is probably too fast but you could fiddle with the LC oscillator section and see if you can get it to go..... alice Author: Bryan Hord >From this explanation it seems like the circuit should work with a higher voltage LED. Has anyone tried to power a blue LED from a single cell? snip%<----------------------------------------------------- >>> On 2/2/98 Pasi T Mustalahti wrote: >>> >>> -------8<-------- >>> > >>> > > ------------------------------------- +U (0.6..1.55 V) {Quote hidden}> | | > R20K || < > | || < > ----------------> || < > | > || < ^^ <---the led > = 10nF | /------>|--| > | ----| BC337 | > | \ | > | | | > -------------------------------------- >>> > > snip %< ---------------------------------------------------- >The circuit is best described as a self-oscillating flyback converter. >Each time the transistor turns on, it charges the transformer with >current until it saturates. When it saturates, the voltage induced in >the base winding decreases, causing the transistor to turn off. The >energy stored in the transformer is then dumped to the load (LED in this >case). > >For a given frequency of operation and transformer core, the circuit will >deliver approximately constant *power* to the load, regardless of the >load voltage. The power is distributed in pulses having the energy that >the transformer core can hold before it saturates. Since it always >charges until it saturates, the output power doesn't depend on the input >voltage, if (and this is a big "if"), the frequency doesn't vary. > >If the DC supplied to the transistor base circuit is adequate, the >circuit will oscillate continuously at the highes practical frequency >(depends on the input voltage and the inductance of the winding). More >likely, Pasi's circuit is running in "relaxation mode". The base current >required by each cycle discharges the capacitor somewhat, to less than >Vbe so the transistor doesn't turn on right away after the transformer >voltage reaches zero (all energy having been delivered to the LED). >There is a delay during which the resistor has to charge up the capacitor >to start the transistor conducting again. So the frequency probably >decreases significantly with input voltage as the current available thru >the resistor decreases. Varying the resistor should vary the frequency, >and thus the brightness of the LED. A diode in parallel with the >transistor base (to keep it from going too far negative) would supply >current to the capacitor while the transistor is off, and probably get >the circuit to oscillate continuously rather than in relaxation mode. >However, the resulting output power would likely be too high, and >difficult to control. > >However, the experiment shows that it had satisfactory performance over >the life of the battery. The self-regulating properties of the circuit >are apparently working well enough. > -- http://www.piclist.com hint: To leave the PICList EraseMEpiclist-unsubscribe-requestspam_OUTTakeThisOuTmitvma.mit.edu>

Consider using an LM3909 LED flasher/oscillator IC. Its not one transistor but it is one device. It needs a 200uf or so cap and a resistor to flash an LED from a 1.5 volt battery. John Pearson wrote: {Quote hidden}> > Am looking for a one transistor LED flasher circuit. Does such an animal > exsist? > > Thank you. > > John > > -- > http://www.piclist.com hint: To leave the PICList > piclist-unsubscribe-requestspam_OUTmitvma.mit.edu -- http://www.piclist.com hint: To leave the PICList @spam@piclist-unsubscribe-requestKILLspammitvma.mit.edu>

I have still got 50 of type 2N4891 for a project that never seen the light of day this was about 1983 Regards Art {Original Message removed}

At 02:12 PM 9/13/00 -0400, you wrote: >UJT relaxation oscillator -- wow its been years! Back in high school I put one of these in a friend's xmas present.. It was about a week before he noticed that it was ticking. Drove him nuts for the next two weeks. The fun part was when he broke the 30ga wire in the wrapping that started it screaming. Subsequent layers were secured with strapping tape. -- Where's dave? http://www.findu.com/cgi-bin/find.cgi?kc6ete-9 -- http://www.piclist.com hint: PICList Posts must start with ONE topic: "[PIC]:" PIC only "[EE]:" engineering "[OT]:" off topic "[AD]:" ad's

A rc phase shift oscillator ought to be able to flash your led. Also a mechanical oscillator with electronic powering (you put the led in the powering circuit). Both have 1-transistor variants. Peter -- http://www.piclist.com hint: PICList Posts must start with ONE topic: "[PIC]:" PIC only "[EE]:" engineering "[OT]:" off topic "[AD]:" ad's