John, Cheers, it's a Gicar 9.0.95.05g -- sits in a cafe-style coffee machine, though this'll only be the first install and the others may be different (but presumably similar) parts. On Wed Dec 17 2014 at 17:02:30 John Syn <[email protected]> wrote:
> > From: Paul Hannah <[email protected]> > Reply-To: "[email protected]" <[email protected]> > Date: Tuesday, December 16, 2014 at 9:27 PM > To: "[email protected]" <[email protected]> > Subject: Re: [beagleboard] Sensing flowmeter / protecting analog input > > John, > > Digital input, hadn't thought of that but it makes sense, but I'm even > less sure of myself in that arena... > > I have to admit first my electronics knowledge is very rusty... > > Maybe I can use a voltage divider after the diode/s to halve that 1.8v+ > down to a safe 1.0v-ish. > > My first thought here is to use a zener diode as in here > http://www.electronics-tutorials.ws/diode/diode42.gif) with a voltage > divider after. > > Is the reverse voltage low enough to be safe with the BBB? > > If not, what if I set up something like this, but make D_Z1 a normal diode > so that the reverse current is completely stopped? > > Again, not interested at all in the quality of the signal as long as I can > determine the number of cycles. > > Sorry for the electronics 101 questions, appreciate all your time. > > BTW, what is the flowmeter part number. Perhaps there is a much simpler > way to interface this to the BBB. > > Regards, > John > > > Cheers, > Paul. > > On Wed Dec 17 2014 at 14:55:09 John Syn <[email protected]> wrote: > >> >> From: William Pretty Security <[email protected]> >> Reply-To: "[email protected]" <[email protected]> >> Date: Tuesday, December 16, 2014 at 7:00 PM >> To: "[email protected]" <[email protected]> >> Subject: RE: [beagleboard] Sensing flowmeter / protecting analog input >> >> Hmm >> >> >> >> Maybe a 1.8v zener ? >> >> I see this recommendation all the time, but it won't work. Look at fig 4 >> in this document for the zener voltage characteristics DDZ9678: >> >> http://www.diodes.com/datasheets/ds30410.pdf >> >> You will see that the zener voltage is at 1.8v when the current is at >> 80uA, but at 100uA, the voltage exceeds the maximum allowed on the ADC >> input. The only way to deal with this situation is to use a proper signal >> conditioner. First start with the voltage range of the input and then scale >> that down with an op-amp. You can also offset the reference to deal with >> negative voltage inputs. >> >> To the OP, you are only using this for counting, why use ADC. Why not >> scale/condition the output of the hall-effect flowmeter and use a digital >> input? >> >> Regards, >> John >> >> Or 1N4007's in series = 1.4V >> >> >> >> "No one could make a greater mistake than he who did nothing because he >> could do only a little." >> >> "All that is necessary for the triumph of evil is that good men do >> nothing" Edmond Burke *(1729 - 1797)* >> >> http://www.packtpub.com/building-a-home-security- >> system-with-beaglebone/book >> >> >> >> *From:* [email protected] [mailto:[email protected] >> <[email protected]>] *On Behalf Of *Paul Hannah >> *Sent:* Tuesday, December 16, 2014 9:09 PM >> *To:* [email protected] >> *Subject:* [beagleboard] Sensing flowmeter / protecting analog input >> >> >> >> Hi, >> >> >> >> I'm looking to build a system to sense 'steps' of a hall-effect flowmeter. >> >> >> >> My first throught is to use a voltage divider and rectifier circuit to >> get down to the 0-1.8v I need. >> >> >> >> The problem I have is that every install may potentially have a different >> input voltage. >> >> >> >> I'm wondering if there's a simpler way to do this. I really only need to >> clip the voltage between 0-1.8v, it doesn't matter if it spends 90% of it's >> time clipped and throws away the negative half of the signal completely as >> I'm only interested in a count. >> >> >> >> The current draw will be in the millivolt-range used by the adc input, so >> it shouldn't need anything too heavy. >> >> >> >> My first thought is a simple voltage regulator set to 1.8v, but I don't >> know enough about them to know whether it's a viable option or which to >> choose. >> >> >> >> Any suggestions? >> >> -- >> For more options, visit http://beagleboard.org/discuss >> --- >> You received this message because you are subscribed to the Google Groups >> "BeagleBoard" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to [email protected]. >> For more options, visit https://groups.google.com/d/optout. >> >> No virus found in this message. >> Checked by AVG - www.avg.com >> Version: 2015.0.5577 / Virus Database: 4253/8748 - Release Date: 12/16/14 >> ------------------------------ >> >> No virus found in this message. >> Checked by AVG - www.avg.com >> Version: 2015.0.5577 / Virus Database: 4235/8735 - Release Date: 12/14/14 >> >> -- >> For more options, visit http://beagleboard.org/discuss >> --- >> You received this message because you are subscribed to the Google Groups >> "BeagleBoard" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to [email protected]. >> For more options, visit https://groups.google.com/d/optout. >> >> -- >> For more options, visit http://beagleboard.org/discuss >> --- >> You received this message because you are subscribed to the Google Groups >> "BeagleBoard" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to [email protected]. >> For more options, visit https://groups.google.com/d/optout. >> > -- > For more options, visit http://beagleboard.org/discuss > --- > You received this message because you are subscribed to the Google Groups > "BeagleBoard" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > For more options, visit https://groups.google.com/d/optout. > > -- > For more options, visit http://beagleboard.org/discuss > --- > You received this message because you are subscribed to the Google Groups > "BeagleBoard" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > For more options, visit https://groups.google.com/d/optout. > -- For more options, visit http://beagleboard.org/discuss --- You received this message because you are subscribed to the Google Groups "BeagleBoard" group. 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