[TriEmbed] I need a circuit to do this....

Chip McClelland chip at mcclellands.org
Wed Jun 22 20:51:39 CDT 2016 

Shane,  very cool. I will do some experiments with the sensor later this
week and then think about the circuit below

You mentioned a microcontroller that can operate at 100uA. Please tell me
more about this.

Thanks,

Chip

On Wednesday, June 22, 2016, Shane Trent <shanedtrent at gmail.com> wrote:

> Chip,
>
> Not a FET but I can do bi-polar as well. A minimalist approach might be
> using a single NPN BJT with a pot and a couple of resistors to trigger INT0
> on a rising edge.
>
> [image: pasted1]
> The BJT conducts and pulls down INT0 anytime the Analog Trigger input is
> approximately 600mV above the pot wiper voltage. Your sensor returns a
> high-voltage when there are no people in the path (max distance). When a
> person enters the sensor area the voltage drops to reflect the now shorter
> distance the target. With proper adjustment this will drop the NPN gate to
> less than 600mV above the pot threshold, turning off the BJT and pulling up
> the INT0 line.
>
> With a 200k pot it would draw about 25uA from a 5V supply. A 100k would
> ensure a larger voltage swing at INT0 but would double your idle current.
> This approach lacks the speed and sensitivity of a proper comparator but
> people move slowly and it sounds like you will have a decent swing when you
> get reflections.
>
> Or you could go new age and add a tiny co-processor to monitor the
> ultrasonic range finder to decide when to wake the main processor. Should
> be possible within your 100uA budget.
>
> Shane
>
> On Wed, Jun 22, 2016 at 11:55 AM Chip McClelland via TriEmbed <
> triembed at triembed.org
> <javascript:_e(%7B%7D,'cvml','triembed at triembed.org');>> wrote:
>
>> All, Thank you for the suggestions.   Here is a consolidated attempt at
>> responding to everyone:
>>
>> 1) Using the AVR comparator - this technique will generate an interrupt
>> but, unfortunately, not one that would wake the micro controller from Sleep
>> mode.  So, will need to put this on in the toolkit for next time.
>>
>> 2) I am using the ATMEGA 328p running at 8Mhz and 3.3V.  Need to generate
>> an interrupt on D3 to wake the controller from SLEEP_MODE_PWR_DOWN.  In
>> this state, with the pins set as INPUTS, I believe they are high impedence.
>>
>> 3) Use case, I am using a 10m outdoor ultrasonic sensor to count folks
>> walking down a gravel road.  The will walk perpendicular to the beam so, I
>> may need to pay with the low pass filter to find a value that dampens the
>> noise but is quick enough.  The sensor does some filtering as well and
>> emits pulses at 6Hz.
>>
>> 4) Thank you all for the comments, I can’t seem to find a latching
>> comparator with the non-inverted latch line so, will simply put in an
>> inverter as suggested.
>>
>> Shane, I am surprised you did not suggest some approach using FETs.  ;-)
>>
>> Thank you all, will share the design and bring it to an upcoming meeting
>> for a demo - provided this works.  Unfortunately, humans are “soft” and I
>> am a bit worried about getting enough of a return to count reliably - will
>> see.
>>
>> Chip
>>
>>
>>
>> > On Jun 22, 2016, at 11:35 AM, triembed-request at triembed.org
>> <javascript:_e(%7B%7D,'cvml','triembed-request at triembed.org');> wrote:
>> >
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>> > than "Re: Contents of TriEmbed digest..."
>> >
>> >
>> > Today's Topics:
>> >
>> >   1. Re: APA102 unsoldering (Brian)
>> >   2. Re: OSH Stencils is offering stainless steel now (Brian)
>> >   3. Re: I need a circuit that can do this..... (Brian)
>> >   4. Re: I need a circuit that can do this..... (Brian)
>> >   5. Re: APA102 unsoldering (Robert Gasiorowski)
>> >
>> >
>> > ----------------------------------------------------------------------
>> >
>> > Message: 1
>> > Date: Wed, 22 Jun 2016 11:13:50 -0400
>> > From: Brian <triembed at undecidedgames.net
>> <javascript:_e(%7B%7D,'cvml','triembed at undecidedgames.net');>>
>> > To: triembed at triembed.org
>> <javascript:_e(%7B%7D,'cvml','triembed at triembed.org');>
>> > Subject: Re: [TriEmbed] APA102 unsoldering
>> > Message-ID: <576AAB2E.7060403 at undecidedgames.net
>> <javascript:_e(%7B%7D,'cvml','576AAB2E.7060403 at undecidedgames.net');>>
>> > Content-Type: text/plain; charset=windows-1252; format=flowed
>> >
>> > Seconded.  Temperature and time is everything.  Not too hot and not too
>> > fast.  The best way to desolder SMT devices is to heat everything, and
>> > do it gradually.  If you have it available, use hot air and don't go
>> > above 280 C.  It will take a fairly long time for the solder to melt,
>> > but the solder also has the highest thermal mass; that is, the plastic
>> > will heat up a lot faster than the metal.  If you're dumping heat in at
>> > 350 C, your plastic bits will hit 350 (and be a molten mess) way before
>> > the metal even gets near 280 (average reflow temp).
>> >
>> > Patience.
>> >
>> > -B
>> >
>> > On 06/22/2016 08:59 AM, Adam Haile via TriEmbed wrote:
>> >> Also, what temp is your iron set to? Realizing that the ChipQuik only
>> >> helps in removal, but since those LEDs are designed to be reflowed,
>> they
>> >> should certainly survive solder melting temp. One thing that might
>> cause
>> >> an issue is using lead-free solder, especially of a cheaper alloy which
>> >> has a much higher temp. If you are using lead-free, try leaded and keep
>> >> the iron <= 600.
>> >>
>> >> On Wed, Jun 22, 2016 at 8:43 AM, Alex Davis via TriEmbed
>> >> <triembed at triembed.org
>> <javascript:_e(%7B%7D,'cvml','triembed at triembed.org');> <mailto:
>> triembed at triembed.org
>> <javascript:_e(%7B%7D,'cvml','triembed at triembed.org');>>> wrote:
>> >>
>> >>    Anyone have any success with unsoldering APA102 LEDs without ruining
>> >>    them? It seems they are made of really shitty thermoplastic which
>> melts
>> >>    at about the melting point of the solder. I had one go bad in my
>> 44x8
>> >>    matrix, and I got it off by using a broad tip to reflow one side at
>> a
>> >>    time while lifting with tweezers. I'd say the package has the
>> thermal
>> >>    resistance of the sort of plastic cheap header strips are made of.
>> It
>> >>    was a ruined plastic blob by time I got it off.
>> >>
>> >>    As to the repair, I am thinking I will just cut an LED off a spare
>> strip
>> >>    and solder it down on top of the blank spot. It won't look as nice
>> but
>> >>    it seems like it will have the highest change of success and of not
>> >>    ruining the mounting strip.
>> >>
>> >>    BTW these APA102 have in and out for both data and clock, and in my
>> case
>> >>    an LED stopped outputting anything on data out, causing the whole
>> rest
>> >>    of the strip to die. Thankfully it was just one unit, but it gives
>> me
>> >>    pause to consider building anything large and expensive out of these
>> >>    things. My setup was working fine before I peeled off the backing
>> tape
>> >>    and glued it on to the enclosure.
>> >>
>> >>    Alex
>> >>
>> >>    --
>> >>    "The theater of noise is proof of our potential."
>> >>    |\ |  (?  \/ |?\  |V| |\ ?|? |?) | \/ | | | |?\ (?   /?  /\ |V|
>> >>    |-||_ (_  /\ |_/ @| | |-| |  | \ | /\ |^| | |_/ (_ . \_  \/ | |
>> >>
>> >>    You won't find me on Facebook.
>> >>
>> >>    _______________________________________________
>> >>    Triangle, NC Embedded Computing mailing list
>> >>    TriEmbed at triembed.org
>> <javascript:_e(%7B%7D,'cvml','TriEmbed at triembed.org');> <mailto:
>> TriEmbed at triembed.org
>> <javascript:_e(%7B%7D,'cvml','TriEmbed at triembed.org');>>
>> >>    http://mail.triembed.org/mailman/listinfo/triembed_triembed.org
>> >>    TriEmbed web site: http://TriEmbed.org
>> >>
>> >>
>> >>
>> >>
>> >> _______________________________________________
>> >> Triangle, NC Embedded Computing mailing list
>> >> TriEmbed at triembed.org
>> <javascript:_e(%7B%7D,'cvml','TriEmbed at triembed.org');>
>> >> http://mail.triembed.org/mailman/listinfo/triembed_triembed.org
>> >> TriEmbed web site: http://TriEmbed.org
>> >>
>> >
>> >
>> >
>> >
>> > ------------------------------
>> >
>> > Message: 2
>> > Date: Wed, 22 Jun 2016 11:15:20 -0400
>> > From: Brian <triembed at undecidedgames.net
>> <javascript:_e(%7B%7D,'cvml','triembed at undecidedgames.net');>>
>> > To: triembed at triembed.org
>> <javascript:_e(%7B%7D,'cvml','triembed at triembed.org');>
>> > Subject: Re: [TriEmbed] OSH Stencils is offering stainless steel now
>> > Message-ID: <576AAB88.3030905 at undecidedgames.net
>> <javascript:_e(%7B%7D,'cvml','576AAB88.3030905 at undecidedgames.net');>>
>> > Content-Type: text/plain; charset=windows-1252; format=flowed
>> >
>> > I just received my first Kapton stencil from them.  I've yet to print
>> > any paste (I ordered the boards at the same time and they're not in
>> > yet), but the workmanship looks great.
>> >
>> > -B
>> >
>> > On 06/22/2016 08:36 AM, Pete Soper via TriEmbed wrote:
>> >> OSH Stencils has started offering four mil stainless steel stencils,
>> and
>> >> is offering a 15% discount through July 5th using coupon code
>> >> "SSLAUNCH15".  Their price is roughly $1.30/inch with a 3/4" minimum
>> >> surround and a $10 minimum total. These folks are south of Salt Lake
>> >> City, with very fast service. More details on their web site:
>> >> http://oshstencils.com
>> >>
>> >> (I have no connection, just been a happy customer of theirs since
>> >> shortly after they started business)
>> >>
>> >> -Pete
>> >>
>> >>
>> >> _______________________________________________
>> >> Triangle, NC Embedded Computing mailing list
>> >> TriEmbed at triembed.org
>> <javascript:_e(%7B%7D,'cvml','TriEmbed at triembed.org');>
>> >> http://mail.triembed.org/mailman/listinfo/triembed_triembed.org
>> >> TriEmbed web site: http://TriEmbed.org
>> >>
>> >
>> >
>> >
>> >
>> > ------------------------------
>> >
>> > Message: 3
>> > Date: Wed, 22 Jun 2016 11:24:06 -0400
>> > From: Brian <triembed at undecidedgames.net
>> <javascript:_e(%7B%7D,'cvml','triembed at undecidedgames.net');>>
>> > To: triembed at triembed.org
>> <javascript:_e(%7B%7D,'cvml','triembed at triembed.org');>
>> > Subject: Re: [TriEmbed] I need a circuit that can do this.....
>> > Message-ID: <576AAD96.7020908 at undecidedgames.net
>> <javascript:_e(%7B%7D,'cvml','576AAD96.7020908 at undecidedgames.net');>>
>> > Content-Type: text/plain; charset=UTF-8; format=flowed
>> >
>> >> ?That part looks like it should work.  You need to be careful of stray
>> >> feedback ?from the output to the inputs so no rats nests of jumpers and
>> >> you need a 0.1 uF ceramic cap shorted across the VDD and ground (like
>> >> right on them not just nearby).
>> >
>> > <pedant_mode>
>> >
>> > Be careful how you use that word, "shorted"... :-)
>> >
>> > Bypass caps can be a few millimeters away and still be ok, though it is
>> > certainly best practice to place them as close to the device's pins as
>> > possible.  On a breadboard, definitely no long jumpers between them and
>> > the device, but being at opposite ends of a 5-hole bus won't be an
>> > issue; there's not enough stray capacitance or inductance in those bus
>> > bars to make any difference, and the wavelengths don't start to get that
>> > short until you hit gigahertz.  Even a couple pre-formed jumpers (the
>> > kind that sit flat against the board) in between won't cause any real
>> > issues.
>> >
>> > </pedant_mode>
>> >
>> >
>> >
>> >
>> >
>> >
>> >
>> > ------------------------------
>> >
>> > Message: 4
>> > Date: Wed, 22 Jun 2016 11:29:42 -0400
>> > From: Brian <triembed at undecidedgames.net
>> <javascript:_e(%7B%7D,'cvml','triembed at undecidedgames.net');>>
>> > To: triembed at triembed.org
>> <javascript:_e(%7B%7D,'cvml','triembed at triembed.org');>
>> > Subject: Re: [TriEmbed] I need a circuit that can do this.....
>> > Message-ID: <576AAEE6.60901 at undecidedgames.net
>> <javascript:_e(%7B%7D,'cvml','576AAEE6.60901 at undecidedgames.net');>>
>> > Content-Type: text/plain; charset=windows-1252; format=flowed
>> >
>> > On 06/22/2016 06:56 AM, Michael Monaghan via TriEmbed wrote:
>> >> The low pass filter on input is an excellent idea in this
>> configuration.
>> >
>> > I'd say it's an absolute must, placed as close to the inputs of the
>> > comparator as possible to reject any EMI along the sensor's leads.  For
>> > a first-order filter (simple RC), I'd suggest a corner frequency around
>> > 10 Hz which will yield a settling time of just under a second (that is,
>> > the average output will lag behind the average input by about a second),
>> > unless you need to measure things that are moving very fast.
>> >
>> > Out of curiosity, what's the application?  If you told us, would you
>> > have to kill us? :-)
>> >
>> >
>> >
>> > ------------------------------
>> >
>> > Message: 5
>> > Date: Wed, 22 Jun 2016 11:35:21 -0400
>> > From: Robert Gasiorowski <rgresume at gmail.com
>> <javascript:_e(%7B%7D,'cvml','rgresume at gmail.com');>>
>> > Cc: "triembed at triembed.org
>> <javascript:_e(%7B%7D,'cvml','triembed at triembed.org');>" <
>> triembed at triembed.org
>> <javascript:_e(%7B%7D,'cvml','triembed at triembed.org');>>
>> > Subject: Re: [TriEmbed] APA102 unsoldering
>> > Message-ID:
>> >       <
>> CAEU50hUR8vv7QUmcZfimdvUP7-crszdNUkkTpmKdahkU0hPeJA at mail.gmail.com
>> <javascript:_e(%7B%7D,'cvml','CAEU50hUR8vv7QUmcZfimdvUP7-crszdNUkkTpmKdahkU0hPeJA at mail.gmail.com');>
>> >
>> > Content-Type: text/plain; charset="utf-8"
>> >
>> > Hot air is the best, but it's not always possible to use it.
>> > When I need to remove SMD part and cannot use hot air, I crush/cut it
>> with
>> > pliers and unsolder each lead separately. This assures least heat
>> stress on
>> > pads.
>> >
>> > On Wed, Jun 22, 2016 at 11:13 AM, Brian via TriEmbed <
>> triembed at triembed.org
>> <javascript:_e(%7B%7D,'cvml','triembed at triembed.org');>>
>> > wrote:
>> >
>> >> Seconded.  Temperature and time is everything.  Not too hot and not too
>> >> fast.  The best way to desolder SMT devices is to heat everything, and
>> do
>> >> it gradually.  If you have it available, use hot air and don't go
>> above 280
>> >> C.  It will take a fairly long time for the solder to melt, but the
>> solder
>> >> also has the highest thermal mass; that is, the plastic will heat up a
>> lot
>> >> faster than the metal.  If you're dumping heat in at 350 C, your
>> plastic
>> >> bits will hit 350 (and be a molten mess) way before the metal even gets
>> >> near 280 (average reflow temp).
>> >>
>> >> Patience.
>> >>
>> >> -B
>> >>
>> >> On 06/22/2016 08:59 AM, Adam Haile via TriEmbed wrote:
>> >>
>> >>> Also, what temp is your iron set to? Realizing that the ChipQuik only
>> >>> helps in removal, but since those LEDs are designed to be reflowed,
>> they
>> >>> should certainly survive solder melting temp. One thing that might
>> cause
>> >>> an issue is using lead-free solder, especially of a cheaper alloy
>> which
>> >>> has a much higher temp. If you are using lead-free, try leaded and
>> keep
>> >>> the iron <= 600.
>> >>>
>> >>> On Wed, Jun 22, 2016 at 8:43 AM, Alex Davis via TriEmbed
>> >>> <triembed at triembed.org
>> <javascript:_e(%7B%7D,'cvml','triembed at triembed.org');> <mailto:
>> triembed at triembed.org
>> <javascript:_e(%7B%7D,'cvml','triembed at triembed.org');>>> wrote:
>> >>>
>> >>>    Anyone have any success with unsoldering APA102 LEDs without
>> ruining
>> >>>    them? It seems they are made of really shitty thermoplastic which
>> >>> melts
>> >>>    at about the melting point of the solder. I had one go bad in my
>> 44x8
>> >>>    matrix, and I got it off by using a broad tip to reflow one side
>> at a
>> >>>    time while lifting with tweezers. I'd say the package has the
>> thermal
>> >>>    resistance of the sort of plastic cheap header strips are made of.
>> It
>> >>>    was a ruined plastic blob by time I got it off.
>> >>>
>> >>>    As to the repair, I am thinking I will just cut an LED off a spare
>> >>> strip
>> >>>    and solder it down on top of the blank spot. It won't look as nice
>> but
>> >>>    it seems like it will have the highest change of success and of not
>> >>>    ruining the mounting strip.
>> >>>
>> >>>    BTW these APA102 have in and out for both data and clock, and in my
>> >>> case
>> >>>    an LED stopped outputting anything on data out, causing the whole
>> rest
>> >>>    of the strip to die. Thankfully it was just one unit, but it gives
>> me
>> >>>    pause to consider building anything large and expensive out of
>> these
>> >>>    things. My setup was working fine before I peeled off the backing
>> tape
>> >>>    and glued it on to the enclosure.
>> >>>
>> >>>    Alex
>> >>>
>> >>>    --
>> >>>    "The theater of noise is proof of our potential."
>> >>>    |\ |  (?  \/ |?\  |V| |\ ?|? |?) | \/ | | | |?\ (?   /?  /\ |V|
>> >>>    |-||_ (_  /\ |_/ @| | |-| |  | \ | /\ |^| | |_/ (_ . \_  \/ | |
>> >>>
>> >>>    You won't find me on Facebook.
>> >>>
>> >>>    _______________________________________________
>> >>>    Triangle, NC Embedded Computing mailing list
>> >>>    TriEmbed at triembed.org
>> <javascript:_e(%7B%7D,'cvml','TriEmbed at triembed.org');> <mailto:
>> TriEmbed at triembed.org
>> <javascript:_e(%7B%7D,'cvml','TriEmbed at triembed.org');>>
>> >>>    http://mail.triembed.org/mailman/listinfo/triembed_triembed.org
>> >>>    TriEmbed web site: http://TriEmbed.org
>> >>>
>> >>>
>> >>>
>> >>>
>> >>> _______________________________________________
>> >>> Triangle, NC Embedded Computing mailing list
>> >>> TriEmbed at triembed.org
>> <javascript:_e(%7B%7D,'cvml','TriEmbed at triembed.org');>
>> >>> http://mail.triembed.org/mailman/listinfo/triembed_triembed.org
>> >>> TriEmbed web site: http://TriEmbed.org
>> >>>
>> >>>
>> >>
>> >> _______________________________________________
>> >> Triangle, NC Embedded Computing mailing list
>> >> TriEmbed at triembed.org
>> <javascript:_e(%7B%7D,'cvml','TriEmbed at triembed.org');>
>> >> http://mail.triembed.org/mailman/listinfo/triembed_triembed.org
>> >> TriEmbed web site: http://TriEmbed.org
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-- 
Sent from my iPhone - please excuse the typos
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