Prev: Microeconomics 5e Jeffrey M. Perloff test bank and solution manual is available for purchase at affordable prices. Contact me at alltestbanks11[at]gmail.com to buy it today.
Next: Essentials of the Legal Environment 2nd Edition 2008 Roger LeRoy Miller Test bank is available for purchase at affordable prices. Contact me at alltestbanks11[at]gmail.com to buy it today.
From: Jim Thompson on 17 Mar 2010 13:40
On Wed, 17 Mar 2010 12:35:09 -0500, "eeboy"
<jason(a)n_o_s_p_a_m.n_o_s_p_a_m.jasonorsborn.com> wrote:

>
>>3. Dump the photodiode current into a tuned LC tank and amplify that
>>with a very low-noise device, probably a jfet. The 4069 will be about
>>the noisiest and least gain-predictable amplifier you can buy for a
>>reasonable amount of money. An LC to ground allows a lot of ambient
>>light signal to get dumped without saturating any amplifier stages.
>>
>
>This sounds interesting to me. So, as I understand it with ambient light
>(DC) I'll have a low impedance path to ground. However, when I am wiggling
>close to the point of resonance I'll begin to see a voltage develop across
>the LC tank as the impedance increases. Correct?
>
>How is the Q of the tuned circuit adjusted?
>
>---------------------------------------
>Posted through http://www.Electronics-Related.com

How much can your 32kHz vary? Modulation rate (pulse widths that need
to be discerned)?

...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

The only thing bipartisan in this country is hypocrisy
From: eeboy on 17 Mar 2010 14:12
>>This sounds interesting to me. So, as I understand it with ambient light
>>(DC) I'll have a low impedance path to ground. However, when I am
wiggling
>>close to the point of resonance I'll begin to see a voltage develop
across
>>the LC tank as the impedance increases. Correct?
>>
>>How is the Q of the tuned circuit adjusted?
>>

>
>How much can your 32kHz vary? Modulation rate (pulse widths that need
>to be discerned)?
>

I wasn't exactly sure what you were specifically asking so hopefully the
answer is in here somewhere... :)

First off, I am actually free to choose any carrier frequency I want. I
chose 32kHz because it was lower than what most of the consumer remotes use
(36-40kHz from what I can tell). Presumably that will make life easier on
me. The transmitter is controlled by a dirt cheap microcontroller which
utilizes a 8MHz RC oscillator as a time base. It's fairly easy to adjust
the transmitter carrier. Given that it is RC based the timing can vary by a
few percent with temperature. I've been doing some tests (heating
up/freezing the transmitter) and can say that at the extremes I am within
3% of the base (room temperature). There will also be a variation from
device to device of course. Although my testing of the variation is not
complete, given the above, I'd like to have a 2kHz window or so.




---------------------------------------
Posted through http://www.Electronics-Related.com
From: Joerg on 17 Mar 2010 14:18
eeboy wrote:
>>> This sounds interesting to me. So, as I understand it with ambient light
>>> (DC) I'll have a low impedance path to ground. However, when I am
> wiggling
>>> close to the point of resonance I'll begin to see a voltage develop
> across
>>> the LC tank as the impedance increases. Correct?
>>>
>>> How is the Q of the tuned circuit adjusted?
>>>
>
>> How much can your 32kHz vary? Modulation rate (pulse widths that need
>> to be discerned)?
>>
>
> I wasn't exactly sure what you were specifically asking so hopefully the
> answer is in here somewhere... :)
>
> First off, I am actually free to choose any carrier frequency I want. I
> chose 32kHz because it was lower than what most of the consumer remotes use
> (36-40kHz from what I can tell). Presumably that will make life easier on
> me. The transmitter is controlled by a dirt cheap microcontroller which
> utilizes a 8MHz RC oscillator as a time base. It's fairly easy to adjust
> the transmitter carrier. Given that it is RC based the timing can vary by a
> few percent with temperature. I've been doing some tests (heating
> up/freezing the transmitter) and can say that at the extremes I am within
> 3% of the base (room temperature). There will also be a variation from
> device to device of course. Although my testing of the variation is not
> complete, given the above, I'd like to have a 2kHz window or so.
>

2kHz may be a bit much for this application. Can't you use a watch
crystal to get the uC stable? Modern ones have internal digital loops to
give you 8MHz or thereabouts of clock.

Then use a watch crystal on the receive end as filter. Cheap, but may
not work well in really frosty temps. And the crystals have to be very
accurate because the bandwidth will be in the order of 10-20Hz. Anyhow,
just as an idea to play with in case all else fails.

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.
From: eeboy on 17 Mar 2010 14:30
>2kHz may be a bit much for this application. Can't you use a watch
>crystal to get the uC stable? Modern ones have internal digital loops to
>give you 8MHz or thereabouts of clock.
>
>Then use a watch crystal on the receive end as filter. Cheap, but may
>not work well in really frosty temps. And the crystals have to be very
>accurate because the bandwidth will be in the order of 10-20Hz. Anyhow,
>just as an idea to play with in case all else fails.

A bit much in the sense that it's not selective enough? Unfortunately the
micro in this app has no such internal loop.

---------------------------------------
Posted through http://www.Electronics-Related.com
From: Joerg on 17 Mar 2010 14:34
eeboy wrote:
>> 2kHz may be a bit much for this application. Can't you use a watch
>> crystal to get the uC stable? Modern ones have internal digital loops to
>> give you 8MHz or thereabouts of clock.
>>
>> Then use a watch crystal on the receive end as filter. Cheap, but may
>> not work well in really frosty temps. And the crystals have to be very
>> accurate because the bandwidth will be in the order of 10-20Hz. Anyhow,
>> just as an idea to play with in case all else fails.
>
> A bit much in the sense that it's not selective enough? ...


Yes.


> ... Unfortunately the micro in this app has no such internal loop.
>

<sigh>

If you must use that one for whatever reason then you are between a rock
and a hard spot. Can you use a 8MHz crystal? Or at least a resonator?

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.
First  |  Prev  |  Next  |  Last
Pages: 1 2 3 4 5 6 7 8 9 10 11 12 13 14
Prev: Microeconomics 5e Jeffrey M. Perloff test bank and solution manual is available for purchase at affordable prices. Contact me at alltestbanks11[at]gmail.com to buy it today.
Next: Essentials of the Legal Environment 2nd Edition 2008 Roger LeRoy Miller Test bank is available for purchase at affordable prices. Contact me at alltestbanks11[at]gmail.com to buy it today.