[TriEmbed] I need a circuit to do this....
Chip McClelland
chip at mcclellands.org
Wed Jun 22 10:54:48 CDT 2016
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 wrote:
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> Today's Topics:
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> 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>
> To: triembed at triembed.org
> Subject: Re: [TriEmbed] APA102 unsoldering
> Message-ID: <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 <mailto: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.
>>
>> _______________________________________________
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>>
>>
>>
>> _______________________________________________
>> Triangle, NC Embedded Computing mailing list
>> TriEmbed at triembed.org
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>
>
>
>
> ------------------------------
>
> Message: 2
> Date: Wed, 22 Jun 2016 11:15:20 -0400
> From: Brian <triembed at undecidedgames.net>
> To: triembed at triembed.org
> Subject: Re: [TriEmbed] OSH Stencils is offering stainless steel now
> Message-ID: <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
>> 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>
> To: triembed at triembed.org
> Subject: Re: [TriEmbed] I need a circuit that can do this.....
> Message-ID: <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>
> To: triembed at triembed.org
> Subject: Re: [TriEmbed] I need a circuit that can do this.....
> Message-ID: <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>
> Cc: "triembed at triembed.org" <triembed at triembed.org>
> Subject: Re: [TriEmbed] APA102 unsoldering
> Message-ID:
> <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>
> 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 <mailto: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 <mailto: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
>>> http://mail.triembed.org/mailman/listinfo/triembed_triembed.org
>>> TriEmbed web site: http://TriEmbed.org
>>>
>>>
>>
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>> Triangle, NC Embedded Computing mailing list
>> TriEmbed at triembed.org
>> http://mail.triembed.org/mailman/listinfo/triembed_triembed.org
>> TriEmbed web site: http://TriEmbed.org
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