Alt-BEAM Archive
Message #12847
To: beam@sgiblab.sgi.com
From: Wilf Rigter Wilf.Rigter@powertech.bc.ca
Date: Thu, 30 Mar 2000 19:28:34 -0800
Subject: [alt-beam] Re: SIMD1/LEDPump Problems
> Hi Roy,
>
> Since we looked at solving your SIM1D1 problems in my earlier post, I
> wondered if the design could be made any simpler. Lo and behold SIMD1V2
> which uses one less component and doesn't require very dark conditions to
> turn on. The two 1N914 diodes in the earlier SIMD1 design can be replaced
> with a single transistor (ie the two diode junctions) but in the process,
> this revision it has really enhanced the behaviour. The PNP, which is any
> high gain transistor including the 2N3906, is ON during charging as the
> solar cell pumps current into the storage cap through the base emitter
> junction. The transistor collector clamps the input of the typical
> oscillator shown to +V until the solar cell output drops below the voltage
> of the cap. In my prototype, the cap is a 1F 2.5V gold cap charged with a
> simulated 5.5V solar cell and the transistor will turn off when the
> charging voltage drops below the fully charged cap voltage (~2.4V). Since
> the PNP operates as a common base amplifier, the voltage gain at the
> collector will cause a rapid voltage transition through the linear region
> of the HC240. When the PNP turns off, the oscillator starts and causes the
> two LEDs at the output to alternately flash. The way the 47uf cap
> discharges through each LED produces a small light explosion and after
> image quite pleasing to the eye. The SIMD1V2 design can also replace the
> two diodes of the original 74HC14 design or control a whole HC240 chip if
> the collector has a 1M pull down resistor to 0V and is connected to the
> tristate enable pins. The SIMD1V2 prototype shown was actively flashing
> the 2 LEDS at a 2Hz rate for over 4 hours on a fully charged (2.4V) cap.
>
> regards
>
> wilf
>
> -----Original Message-----
> From: Dye, Roy [SMTP:rdye@logicaldimensions.com]
> Sent: Wednesday, March 29, 2000 1:22 PM
> To: 'Wilf Rigter'
> Subject: RE: SIMD1/LEDPump Problems
>
> Wilf,
>
> I am using the circuit you sent to the BEAM list, LEDPUMP2.GIF, around mid
> January. I pretty much built this circuit to the diagram, with exceptions
> to the solar cell, cap, diode and LEDs that I mentioned in my earlier
> message. Are there additional circuitry or components that this circuit
> needs?
>
> I was hoping to build a circuit that charges all day, and blinks all night
> and thought that this was the one to use.
>
> Please advise.
> Roy
>
12848 Thu, 30 Mar 2000 20:00:52 -0800 RE: Emerging Growth Stocks "Baysinger, Gary"
>
>
> -----Original Message-----
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> Sent: Thursday, March 30, 2000 2:30 AM
> To: cl600@post.com
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