Alt-BEAM Archive

Message #03228



To: "'Nigel Joyce'" nigel.joyce@qr.com.au,
From: Wilf Rigter Wilf.Rigter@powertech.bc.ca
Date: Thu, 13 May 1999 07:34:51 -0700
Subject: [alt-beam] Re: My Pagerbot


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=20
fax: (604)590-3411

> -----Original Message-----
> From: Nigel Joyce [SMTP:nigel.joyce@qr.com.au]
> Sent: Wednesday, May 12, 1999 6:24 PM
> To: Wilf Rigter
> Cc: BEAM Mail
> Subject: Re: My Pagerbot
>=20
> Hey Wilf,
> So to take that circuit you sent, and add the stuff you told me about
> earlier the=20
> improved FLED photovore would look like this?
> << File: XFled1.bmp >>=20
> Sorry about the quality, I have to draw and scan.
> Is this what you meant with the reverse leakage of the photodiodes?
> =A0
> Thanks for all your help
> ---Buzz---
> =A0
> > Hi Nigel.
> >=20
> > > Here is a little reworked FLED circuit I call the XLED (cause =
it's a
> cross
> > > of many prior FLED=A0 circuits ) . I have=A0 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
> > >=20
> > regards=A0=A0=20
> > > Wilf Rigter
>=20
> > > 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.=A0=A0=20
> > >=20
> > > Wilf Rigter
>=20
> > > Wilf,
> > > So the pot would go between the anode sides of the PD's=A0 which =
are
> > > in
> > > parallel with the feeler switches?
> > >=20
> > > Oh, one other question,=A0 I have not come across a site =
explaning the
> > > function of the 2.2k resistor on a SE,=A0 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.
> > >=20
> > > ---Buzz---
> > >=20
> > > > yes, you need the pot for adjusting the FLED thresholds.
> > > > Let us know the result OK?
> > > >
> > > > regards
> > > > Wilf Rigter
> > > > >
> > > > > Ok, thanks,=A0 I will try it tonight,=A0 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=A0switches.
> > > > > > 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=A0like this.
> > > > > > >=A0 << 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---
>=20

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