Alt-BEAM Archive
Message #03245
To: "Wilf Rigter" Wilf.Rigter@powertech.bc.ca
From: "Nigel Joyce" nigel.joyce@qr.com.au
Date: Fri, 14 May 1999 08:56:52 +1000
Subject: [alt-beam] Re: My Pagerbot
Wilf,
Can you test it with about a 2.4v supply? I started boarding the
circuit last night and found I was out of FLED's, so I off to the shop today
for more gear.
Cya
---Buzz---
> Hi Nigel,
>
> I have tested the XFLED idea and the theoretical dropout voltages are
(note
> Steve Bolt) spot on.
> I don't have a solar cell so I used a 10K resistor in series with 5V. If
> you use the LED in series with the 3906 base then the FLED must be put in
> series with a RED LED or a forward PD to raise the trigger voltage or else
> the turn off is too close to the trigger voltage.
> I have not yet tried the reverse PDs in parallel with the switches but you
> may be better off with the original forward biased configuration in series
> with the FLEDs. I will check your circuit tonight and let you know.
>
> regards
>
> Wilf Rigter mailto:wilf.rigter@powertech.bc.ca
> tel: (604)590-7493
> fax: (604)590-3411
> >
> > Hey Wilf,
> > So to take that circuit you sent, and add the stuff you told me about
> > earlier the
> > improved FLED photovore would look like this?
> > << File: XFled1.bmp >>
> > Sorry about the quality, I have to draw and scan.
> > Is this what you meant with the reverse leakage of the photodiodes?
> >
> > Thanks for all your help
> > ---Buzz---
> >
> > > Hi Nigel.
> > >
> > > > Here is a little reworked FLED circuit I call the XLED (cause it's a
> > cross
> > > > of many prior FLED circuits ) . I have not tested it but it should
> > work
> > > > . The 1K resistor can be adjusted for motor (size) inrush current
> > > > requirements and the 10K resistor can be adjusted more or less
> > > > independendly to set the sensitivity. Using a diode makes the
dropout
> > > > voltage about 1.5V and the LED about 2.1V
> > > >
> > > regards
> > > > Wilf Rigter
> >
> > > > The pot goes between the cathodes and the anodes go to gnd. The
> > switches
> > > > go across the PDs. The PD no operates in the reverse leakage mode
and
> > the
> > > > PD with the highest leakage (light) will cause that SE to fire
first.
> > The
> > > > 2.2K resistor has two effects during charging it acts like a load
> > resistor
> > > > for the FLED and the current through the FLED must reach 2.5mA
before
> > > > enany current is supplied to the base of the 2N3906. After the
2N3906
> > > > turns on and also turns on the 2N3904 then the 2.2K resistor
supplies
> > the
> > > > base current for the 2N3906.You can improve the performance by
> > replacing
> > > > the 2.2K with a 1K resistor in series with a diode and a parallel
10K
> > > > resistor in parallel with both. The cathode of the diode goes to the
> > > > collector of the 2N3904. Now the loading during charging is set by
the
> > 10K
> > > > resistor and the base current for the 2N3906 is set by the diode and
> > 1K
> > > > resistor to inprove saturation and drive bigger motors. I will send
> > you a
> > > > little schematic of that in a couple of hours.
> > > >
> > > > Wilf Rigter
> >
> > > > Wilf,
> > > > So the pot would go between the anode sides of the PD's which are
> > > > in
> > > > parallel with the feeler switches?
> > > >
> > > > Oh, one other question, I have not come across a site explaning the
> > > > function of the 2.2k resistor on a SE, do you know of a site that
> > > > explains
> > > > this as I really want to understand the effect of small changes to
> > > > SE's to
> > > > suit different requirements.
> > > >
> > > > ---Buzz---
> > > >
> > > > > yes, you need the pot for adjusting the FLED thresholds.
> > > > > Let us know the result OK?
> > > > >
> > > > > regards
> > > > > Wilf Rigter
> > > > > >
> > > > > > Ok, thanks, I will try it tonight, do you still use the pot?
> > > > > > Blue Skies
> > > > > > ---Buzz---
> > > > > >
> > > > > > > I don't know what the value of the pot is or what photodiodes
> > > > (PD) you use
> > > > > > > but try this: place the PDs reverse biased in parallel with
> > > > the switches.
> > > > > > > This means the cathode (stripe) is facing up. Depending on the
> > > > > > sensitivity of the PD, this should work quite well.
> > > > > > >
> > > > > > > enjoy
> > > > > > > Wilf Rigter
> > > > > >
> > > > > > > > OK Guy's
> > > > > > > > Here's the problem, I have to use a FLED photopopper circuit
> > > > because of
> > > > > > > > the shortage of 1381's in this part of the world };-) the 1
> > > > I used looks like this.
> > > > > > > > << File: FLEDPV.gif >>
> > > > > > > > In the picture from my previous post on this thread, you see
> > > > the solar panel, it is from a calculator and produces about 2.3v.
now
> > > > the FLED won't fire at that voltage or the charge rate is too slow
to
> > > > fire the FLED, combined with that is the "eyes" (in the above
> > > > pic, the eyes are
> > > > > > > > next to the pot), which are in series with the FLED raising
> > > > the total
> > > > > > > > threshold voltage to about 3.1v (about 2.4v for the FLED +
> > > > about 0.7v for
> > > > > > > > the IR Detecting Diodes) Now as you can see that won't work
> > > > because the solar panel never reaches that high. Is there any way I
> > can
> > > > Lower the
> > > > > > > > threshold voltage to about a total of 2.0v ?
> > > > > > > > Note: I may not have the jargon right, but I know what I
> > > > mean };-)
> > > > > > > > Thanks and
> > > > > > > > Blue Skies
> > > > > > > > ---Buzz---
> >
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