opto circuit
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Posts: 46,084
Hi,
I'm new to the basic stamp and haven't used one yet. I see the posts
about burning up outputs, is it possible to add a optical isolator
to the outputs and save the output?
Later
I'm new to the basic stamp and haven't used one yet. I see the posts
about burning up outputs, is it possible to add a optical isolator
to the outputs and save the output?
Later
Comments
wrote:
> Hi,
> I'm new to the basic stamp and haven't used one yet. I see the
posts
> about burning up outputs, is it possible to add a optical isolator
> to the outputs and save the output?
> Later
Sure, but the need is not that great.
The main thing is to think about what you are doing, and protect what
is needed.
Imagine you have an pot in your circuit, powered from the power
supply. a 10k ohm resistor between the pot and stamp. calculate the
power available with a 5 volt power thru the 10k
ditto for a 10k and a switch.
Calculate the power needed to light an led.
If you use a PN2222 to power a relay, your stamp pin power ends at
the 2222. From there the relay can kill the 2222 but not your pin.
If you follow the logic, 99.9% of your pins end with a resistor as
the limiting device, or some logic device. Using an opto on an LED
on board is kinda silly.
The problem comes when one is not careful and plugs the wrong thing
in to the wrong place.
But, as you mention, opto isolators offer protection for those
occasional circuits.
My philosophy is that nothing on-board is protected beyond normal
resistors as current limiting, and everything off-board is protected
in some way or another, with worst possible event as the threshold
for protection. (I don't plan for lightning strikes, but do plan for
110 VAC on 24VAC lines.)
I have a machine with an end switch that indicates it travels too
far. All the power is run next to all the control lines and sensor
lines. Well, all the 110AC is in a shielded cable and all the
sensors are in another shielded cable, but in that cable are mixed
24VAC lines and 12Vdc lines.
In the event something goes wrong, the potential for 110VAC or 24VAC
back to the control logic is a real threat.
In sucha a case, NOT using opto's would be silly.
Actually, the inputs and outputs are fused AND isolated.
I don't mind terribly losing a switch and enjoy losing a fuse, but I
would really hate to have to replace a multi-conductor flex cable for
some simple problem.
Also, doing a forensic review of a board that has a trace burned from
the output back to the power supply makes one a little sick.
Espically when you realize how simple the fix would have been.
Bottom line is common sense.
Dave
resistor (220 ohms) will save your Stamp from accidents. We now build
in 220 ohm resistors on every IO pin on the BS2 Homework Board and the
BS1 Project Board. Note that both of these boards use built-in Stamp
circuits, so if you're using a Stamp module or stock BOE, you'll need to
add the 220s yourself.
I carry as small plastic box of resistors. The box has five
compartments. Here's how the box is stocked and why:
220 - pin protection
470 - LEDs (a few)
1K - LEDs (a bunch, ie 7-segment)
4.7K - I2C and 1-Wire buss pull-ups
10K - switch input pull-up/pull-down
-- Jon Williams
-- Parallax
Original Message
From: fatboyhd2k [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=ny45KPDoCYonACtc6GD_OoZ40ooxCNIbtY9mkxl3m9BJ5aA6rJDcwP93w2L2jl29pinrnDuw8n2jhy2OJfE]fatboyhd2k@y...[/url
Sent: Sunday, January 11, 2004 12:13 PM
To: basicstamps@yahoogroups.com
Subject: [noparse][[/noparse]basicstamps] opto circuit
Hi,
I'm new to the basic stamp and haven't used one yet. I see the posts
about burning up outputs, is it possible to add a optical isolator
to the outputs and save the output?
Later
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wrote:
> Of course you can, but most of the time the addition of a simple
series
> resistor (220 ohms) will save your Stamp from accidents. We now
build
> in 220 ohm resistors on every IO pin on the BS2 Homework Board and
the
> BS1 Project Board. Note that both of these boards use built-in
Stamp
> circuits, so if you're using a Stamp module or stock BOE, you'll
need to
> add the 220s yourself.
>
> I carry as small plastic box of resistors. The box has five
> compartments. Here's how the box is stocked and why:
>
> 220 - pin protection
> 470 - LEDs (a few)
> 1K - LEDs (a bunch, ie 7-segment)
> 4.7K - I2C and 1-Wire buss pull-ups
> 10K - switch input pull-up/pull-down
>
>
> -- Jon Williams
> -- Parallax
>
And I thought pocket protectors showed who were the brainy geeks : )
If one was to try use an opto isolator how would they go about it?
I have read a few pages about them and it seems sort of confusing is
there a straight forward way to impliment them with the stamp + is
there a prefered opto isolator that would be ideal for use with the
stamp??
Rgds
Arridh
--- In basicstamps@yahoogroups.com, "Jon Williams" <jwilliams@p...>
wrote:
> Of course you can, but most of the time the addition of a simple
series
> resistor (220 ohms) will save your Stamp from accidents. We now
build
> in 220 ohm resistors on every IO pin on the BS2 Homework Board and
the
> BS1 Project Board. Note that both of these boards use built-in
Stamp
> circuits, so if you're using a Stamp module or stock BOE, you'll
need to
> add the 220s yourself.
>
> I carry as small plastic box of resistors. The box has five
> compartments. Here's how the box is stocked and why:
>
> 220 - pin protection
> 470 - LEDs (a few)
> 1K - LEDs (a bunch, ie 7-segment)
> 4.7K - I2C and 1-Wire buss pull-ups
> 10K - switch input pull-up/pull-down
>
>
> -- Jon Williams
> -- Parallax
>
>
>
Original Message
> From: fatboyhd2k [noparse][[/noparse]mailto:fatboyhd2k@y...]
> Sent: Sunday, January 11, 2004 12:13 PM
> To: basicstamps@yahoogroups.com
> Subject: [noparse][[/noparse]basicstamps] opto circuit
>
>
> Hi,
> I'm new to the basic stamp and haven't used one yet. I see the
posts
> about burning up outputs, is it possible to add a optical isolator
> to the outputs and save the output?
> Later
>
>
>
> To UNSUBSCRIBE, just send mail to:
> basicstamps-unsubscribe@yahoogroups.com
> from the same email address that you subscribed. Text in the
Subject
> and Body of the message will be ignored.
>
>
> Yahoo! Groups Links
>
> To visit your group on the web, go to:
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>
> To unsubscribe from this group, send an email to:
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>
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