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Science Forum Index » Optics Forum » Photo Protection circuit
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| Barry |
 Posted: Thu Oct 30, 2003 3:53 pm |
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Guest
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Hi again all,
I've finished building my photodiode protection circuit and I'm
currently testing it -
My results so far are here - http://baz.perlmonk.org/circuit.html
I'm wondering what else I might test (with regard to my circuit) to
ensure that I wont damage my photodiode? Are my results consistent
with my circuit and will those small "power on" transients offer any
problems for my photodiode?
The power supply I'm using is the Calex BPS4000. I also tried
connecting my circuit to the Farnell TOPS1 - 200mA, but immediately
after switching on the supply I got a smell of burning. The fault
occurred at the 100 Ohm resistor (Collector to 15V). I quickly
switched off the supply and measured the voltage across this resistor
- It was still working correctly, and thankfully so is the rest of my
circuit.
Why is the -15Volt rail taking so log to discharge with respect to the
15Volts?
This is my photodiode spec -
http://www.afonics.com/PDF%20data%20sheets/PXP/pxp0017.pdf
I've posted this on the electonics design forum also.
Thanks for your help,
Barry. |
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| Phil Hobbs |
| Posted: Thu Oct 30, 2003 4:29 pm |
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Barry wrote:
Quote:
Why is the -15Volt rail taking so log to discharge with respect to the
15Volts?
Because it has the same size filter cap as the +15V, but you're drawing
less current out of it.
Cheers,
Phil Hobbs |
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| Barry |
| Posted: Fri Oct 31, 2003 8:29 am |
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Thanks guys, I've updated -
http://baz.perlmonk.org/circuit.html
to include the op-amp output.
What else should I check to insure that it is now safe for me to
connect my photodiode to my circuit, or do you think from the above
analysis that it is now safe?
This is my photodiode spec -
http://www.afonics.com/PDF%20data%20sheets/PXP/pxp0017.pdf
Thanks for your help,
Barry.
Phil Hobbs <pcdhSpamMeSenseless@us.ibm.com> wrote in message news:<3FA182B3.9EDB6F8@us.ibm.com>...
Quote: Barry wrote:
Why is the -15Volt rail taking so log to discharge with respect to the
15Volts?
Because it has the same size filter cap as the +15V, but you're drawing
less current out of it.
Cheers,
Phil Hobbs |
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| Al |
| Posted: Fri Oct 31, 2003 8:57 am |
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Guest
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In article <3FA182B3.9EDB6F8@us.ibm.com>,
Phil Hobbs <pcdhSpamMeSenseless@us.ibm.com> wrote:
Quote: Barry wrote:
Why is the -15Volt rail taking so log to discharge with respect to the
15Volts?
Because it has the same size filter cap as the +15V, but you're drawing
less current out of it.
Cheers,
Phil Hobbs
Maybe. The most negative supply in a system has to be the first to power
up and the last to power off. Why, because otherwise many devices will
go into "latchup" and destroy themselves. Modern devices have more
protection against latchup, but don't count on it.
Al
--
There's never enough time to do it right the first time....... |
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| Barry |
| Posted: Tue Nov 04, 2003 5:24 am |
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Guest
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Established the reason for the switching spikes in my circuit. More
details here -
http://baz.perlmonk.org/circuit.html
Anyway, I think I'm now ready to hook up my photodiode to the circuit.
If anyone can think of a reason not to, or one last test I might
perform before the act, then please let me know. My email address is
-barrygriffinNO_SPAM@mail.ie (remove N0_SPAM).
And my InGaAs photodiode spec is here -
http://www.afonics.com/PDF%20data%20sheets/PXP/pxp0017.pdf
Thanks for everything,
Barry.
Al <no.spam@here.com> wrote in message news:<no.spam-871210.08571131102003@news.verizon.net>...
Quote: In article <3FA182B3.9EDB6F8@us.ibm.com>,
Phil Hobbs <pcdhSpamMeSenseless@us.ibm.com> wrote:
Barry wrote:
Why is the -15Volt rail taking so log to discharge with respect to the
15Volts?
Because it has the same size filter cap as the +15V, but you're drawing
less current out of it.
Cheers,
Phil Hobbs
Maybe. The most negative supply in a system has to be the first to power
up and the last to power off. Why, because otherwise many devices will
go into "latchup" and destroy themselves. Modern devices have more
protection against latchup, but don't count on it.
Al |
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