[optacon-l] Re: Replacement light bulb for optacon camera
- From: "Pentronics" <service@xxxxxxxxxxxxxxxxx>
- To: <optacon-l@xxxxxxxxxxxxx>
- Date: Wed, 15 Jun 2011 15:16:32 +1000
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Parallel. Looks like this under the paint
Pentronics
33B Sheppard Road
Emu Plains
NSW 2750
Tel. +61 2 4735 7355
Email. service@xxxxxxxxxxxxxxxxx
Web. www.pentronics.com.au
-----Original Message-----
From: optacon-l-bounce@xxxxxxxxxxxxx [mailto:optacon-l-bounce@xxxxxxxxxxxxx]
On Behalf Of johnobuttons@xxxxxxxxxxx
Sent: Wednesday, 15 June 2011 2:46 PM
To: optacon-l@xxxxxxxxxxxxx
Subject: [optacon-l] Re: Replacement light bulb for optacon camera
Hi Nigel,
I think you're right about LED's being more trouble than they are worth in
this application.
I looked at how the bulbs are hooked up today, but I can't see the
connections very well because the wires have been
coated with black paint, presumably to reduce stray reflections in the
camera.
I measured the supply voltage as 4.8 V which is consistent with using a 5V
bulb.
There is also a series resistor of 15 ohms.
Here's where it gets confusing. I assume the bulbs are in parallel since
one is lite and the other isn't.
However it's conceivable that they were in series and that someone put a
shunt across a burned out bulb.
I'm proceeding slowly so as to "do no harm".
Does anyone know for sure if bulbs are parallel?
John
-----Original Message-----
From: optacon-l-bounce@xxxxxxxxxxxxx [mailto:optacon-l-bounce@xxxxxxxxxxxxx]
On Behalf Of Pentronics
Sent: Tuesday, June 14, 2011 9:14 PM
To: optacon-l@xxxxxxxxxxxxx
Subject: [optacon-l] Re: Replacement light bulb for optacon camera
HI John,
They look like they might do the job. I think you are going to run into all
sorts of trouble trying to use LED's. When the lamps are adjusted correctly
they pretty much just glow. They are at nowhere near their maximum
brightness capability. I don't think you will be able to get enough control
of an LED to run it like this. I'm not sure if would have any affect but
there would be a vast difference in colour temperature.
Try the incandescents first.
Nigel
Pentronics
33B Sheppard Road
Emu Plains
NSW 2750
Tel. +61 2 4735 7355
Email. service@xxxxxxxxxxxxxxxxx
Web. www.pentronics.com.au
-----Original Message-----
From: optacon-l-bounce@xxxxxxxxxxxxx [mailto:optacon-l-bounce@xxxxxxxxxxxxx]
On Behalf Of johnobuttons@xxxxxxxxxxx
Sent: Tuesday, 14 June 2011 10:04 AM
To: optacon-l@xxxxxxxxxxxxx
Subject: [optacon-l] Re: Replacement light bulb for optacon camera
Thanks Nigel,
I see what you're getting at regarding LED intensity.
Typically it's necessary to use a current regulated power supply to adjust
LED brightness, whereas incandescent bulbs generally use a voltage regulated
power supply. So it might be possible to add an adjustable current limiter,
but it's much easier if I can find an incandescent bulb.
I once built a current regulated power supply to dim an LED for use as a
microscope illuminator and it worked out very well.
Actually, I'd be very happy if I could just find a supply of replacement
bulbs on the internet. This is about as close to what Dave described as I
was able to find.
http://www.bulbs.com/T--Type/Under_5W/Lead_wires/results.aspx?Ns=P_Wattage+S
ort|0&pid=279
The diameter of the first bulb is 0.125 inch which is about 3 mm Perhaps
that's the right one??
Thanks for all the help. I've enjoyed learning about the optacon!
John
-----Original Message-----
From: optacon-l-bounce@xxxxxxxxxxxxx [mailto:optacon-l-bounce@xxxxxxxxxxxxx]
On Behalf Of Pentronics
Sent: Monday, June 13, 2011 4:32 PM
To: optacon-l@xxxxxxxxxxxxx
Subject: [optacon-l] Re: Replacement light bulb for optacon camera
Hi John,
Dave answered your email before I got the chance - it was a holiday weekend
here. The one thing I will add is that LED's will not work. It will not be
possible to vary the lamp intensity to achieve the correct threshold range.
The brightness of the lamps is critical for this.
The correct threshold setting is achieved by setting the Threshold control
on the front panel to approximately 10 o'clock, the camera zoom to maximum
and adjusting the Intensity pot VR2, (in the front right hand corner of the
power and timing board), so that approximately 50% of stimulators are
driver. This will occur in the top and bottom potions of the array and
progress to the centre as the brightness is adjusted.
Nigel Herring
Pentronics
33B Sheppard Road
Emu Plains
NSW 2750
Tel. +61 2 4735 7355
Email. service@xxxxxxxxxxxxxxxxx
Web. www.pentronics.com.au
-----Original Message-----
From: optacon-l-bounce@xxxxxxxxxxxxx [mailto:optacon-l-bounce@xxxxxxxxxxxxx]
On Behalf Of johnobuttons@xxxxxxxxxxx
Sent: Monday, 13 June 2011 10:29 AM
To: optacon-l@xxxxxxxxxxxxx
Subject: [optacon-l] Replacement light bulb for optacon camera
Hello,
I trying to fix an optacon for a friend.
After removing the ancient battery, the unit appeared to be working.
However one of the two light bulbs in the camera (scanning) unit is
Not lighting.
Can anyone give me any advice on replacing this bulk.
Has anyone ever tried using an LED replacement?
Thanks for any and all help!
John Hamilton
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