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'[PIC:]Need solid +5VDC level for input to PIC'
2003\11\21@194637 by Stephen D. Barnes

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Hi all,
I am working with an optical encoder which outputs a voltage
between +0.35VDC and +1VDC. What is the easiest low
component count method for getting a clean 0V to 5V pulse
from this to use as an input to the PIC?
Thanks.

Regards,
Stephen D. Barnes


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2003\11\21@195921 by Daniel Imfeld

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From: "Stephen D. Barnes" <.....stephendbarnesKILLspamspam@spam@HOTPOP.COM>
> Hi all,
> I am working with an optical encoder which outputs a voltage
> between +0.35VDC and +1VDC. What is the easiest low
> component count method for getting a clean 0V to 5V pulse
> from this to use as an input to the PIC?
> Thanks.
>
> Regards,
> Stephen D. Barnes

It seems like a comparator would work well.  Just put 0.7 V or so at one
input, and the encoder's output at the other input.

Daniel Imfeld

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2003\11\21@201544 by D Yates

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The first way that jumps to mind is the old-fashioned transistor switch.  It
only needs three parts, is available off the shelf, easy to assemble, and
its cheap.  You said it outputs a voltage, so you could probably use a
mosfet instead of a bipolar.  Or a comparator would probably work great,
just set the - input to your trigger voltage and put the encoder on the +.



: Hi all,
: I am working with an optical encoder which outputs a voltage
: between +0.35VDC and +1VDC. What is the easiest low
: component count method for getting a clean 0V to 5V pulse
: from this to use as an input to the PIC?
: Thanks.
:
: Regards,
: Stephen D. Barnes

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2003\11\21@202830 by Stephen D. Barnes

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> The first way that jumps to mind is the old-fashioned transistor switch.  It
> only needs three parts, is available off the shelf, easy to assemble, and
> its cheap.  You said it outputs a voltage, so you could probably use a
> mosfet instead of a bipolar.  Or a comparator would probably work great,
> just set the - input to your trigger voltage and put the encoder on the +.
>
>
>
> : Hi all,
> : I am working with an optical encoder which outputs a voltage
> : between +0.35VDC and +1VDC. What is the easiest low
> : component count method for getting a clean 0V to 5V pulse
> : from this to use as an input to the PIC?
> : Thanks.
> :
> : Regards,
> : Stephen D. Barnes

Would a 555 timer in monostable mode work? I do have many of these hanging around?

Regards,
Stephen D. Barnes

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2003\11\21@204037 by Russell McMahon

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> I am working with an optical encoder which outputs a voltage
> between +0.35VDC and +1VDC. What is the easiest low
> component count method for getting a clean 0V to 5V pulse
> from this to use as an input to the PIC?

If those voltages are reliable levels then a transistor will work well with
3 resistors.

If they aren't reliable then a bit of design will still produce the goods.
Ask with more details if this is the case.

A 555 as suggested MAY work but needs design.

TRANSISTOR. DESIGN

   Cheap. Easy. Compact. Learn something. Works.

NPN small signal. Just about anything. (2N2222 or whatever)

R1 Input resistor 10k to 100K from input signal to base.
R2 Pulldown / leakage shunt 100k to 1 megohm base to ground.
R3 Collector resistor 10k to 100k collector to Vdd.
PIC pin to Vdd.

R2 can perhaps be omitted but its good to have it.

Cheap. Simple. Works if voltages are as stated.

R1 larger makes less load on signal
R2 at least 10 x R1 (more OK)
R3 could be 1M probably but 100K OK.

If this signal is very high speed things will get more complex. The above
should probably work at eg 10 kbps without a thought.
Maybe at 100 kbps
Almost certainly not at 1 Mbps



       Russell McMahon

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2003\11\21@205037 by John J. McDonough

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Well, first of all, you're not going to get 0 with anything simple, but for
a PIC input, you don't need +5 either.  Wouldn't a simple transistor do?

--McD

{Original Message removed}

2003\11\21@205247 by Stephen D. Barnes

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{Quote hidden}

The speed of the encoder will never reach those speeds. This sound like it will do the
trick and I do have a handfull of 2SC536 NPN transistors (TO-92)!
Thanks to everyone for their input....now on to the breadboarding!

Regards,
Stephen D. Barnes

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2003\11\22@004105 by Herbert Graf

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> Hi all,
> I am working with an optical encoder which outputs a voltage
> between +0.35VDC and +1VDC. What is the easiest low
> component count method for getting a clean 0V to 5V pulse
> from this to use as an input to the PIC?
> Thanks.

       Easiest would be an NPN transistor, two resistors and the transistor is all
you'd need. TTYL

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2003\11\22@021350 by ahid Sheikh

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> It seems like a comparator would work well.  Just put 0.7 V or so at
> one input,and the encoder's output at the other input.

A comparator was the first thing I thought of too. If you use a PIC that
already has a comparator you won't need any external components.

Shahid

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2003\11\22@073107 by Olin Lathrop

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Stephen D. Barnes wrote:
> I am working with an optical encoder which outputs a voltage
> between +0.35VDC and +1VDC. What is the easiest low
> component count method for getting a clean 0V to 5V pulse
> from this to use as an input to the PIC?

An opamp and a few resistors can do this.

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(978) 742-9014, http://www.embedinc.com

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2003\11\22@080255 by Olin Lathrop

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>> I am working with an optical encoder which outputs a voltage
>> between +0.35VDC and +1VDC. What is the easiest low
>> component count method for getting a clean 0V to 5V pulse
>> from this to use as an input to the PIC?
>
> An opamp and a few resistors can do this.

After seeing other replies I realized the OP wanted to compare the signal to
a threshold, not present it to an A/D input.  Sorry.

The best solution for that is to use a PIC with a comparator.  That failing,
the next easiest circuit depends on the impedence of the input signal and
speed requirement.  A single transistor and resistor could be good enough if
the PIC input has an internal pullup.  350mV to 1V is a very convenient
range for detecting with a silicon transistor, which would has a threshold
of around 700mV.


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(978) 742-9014, http://www.embedinc.com

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2003\11\23@014759 by Stephen D. Barnes

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Hello everyone,
First, I would like to thank all who have replied to my posts concerning this thread and
the one about the MS mouse schematics. I have been trying to hack a mouse to use as wheel
encoders on a hobby robot. The voltage levels from the detectors in the mouse (0.35 to
1.00 vdc) had me very confused. I have just found out that the MS mouse is pulsing the
emitters at 38 or 40 KHz (not sure which 'cause I do not have a scope handy at the
moment). I connect the detector output to the timer1 input configured for external clock
on a 18F4320. Connected portB to led's and watched the count as I rotate the toothed
wheel. If I stop the wheel so that IR passes to the detector, BOOM, it it increments
timer1 with no wheel rotation. Block the detector and the increment stops! I'll have to
remove the Zilog chip from the mouse and connect the IR emitters for continuous operation.
I was actually reading a high pulse rate with a meter set to DC volts and was reading idle
current/voltage and then approx. 40KHz pulses which averaged out to be about 1 VDC!
Learned a valuable lesson from this one. Again, thanks for all the help folks.

Regards,
Stephen D. Barnes

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2003\11\24@055253 by Alan B. Pearce

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>> I am working with an optical encoder which outputs a voltage
>> between +0.35VDC and +1VDC. What is the easiest low
>> component count method for getting a clean 0V to 5V pulse
>> from this to use as an input to the PIC?
>> Thanks.
>>
>> Regards,
>> Stephen D. Barnes
>
>It seems like a comparator would work well.  Just put 0.7 V or so at one
>input, and the encoder's output at the other input.

Use a PIC with a comparator input, and then you do not need any extra
components? Most of the new ones have comparators.

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