Yes, that sounds exactly like the device. Awesome, didn't even know such a beast existed. Will do my reading tonight.
Thanks again, Paul. On Wed Dec 17 2014 at 17:47:20 John Syn <[email protected]> wrote: > From: Paul Hannah <[email protected]> > Reply-To: "[email protected]" <[email protected]> > Date: Tuesday, December 16, 2014 at 10:26 PM > > To: "[email protected]" <[email protected]> > Subject: Re: [beagleboard] Sensing flowmeter / protecting analog input > > 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. > > OK, I couldn't find a data sheet, but I think this is a three pin device, > GND, POWER (4.5 - 20V) and PULSE. If this is correct, then all you need is > a resistor divider as you suggested and a schmitt trigger to clean up the > signal and then feed this directly into one of the GPIO pins. The schmitt > trigger should be powered from VDD_3V3B and enabled with SYS_RESETn. > > Regards, > John > > > 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:beagleboard@ >>> googlegroups.com <[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. > 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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