V out = Vin x [R1/(R1+R2)] So you are giving it 5 volts full scale and you need .1 volt to represent full scale.
V out/ V in = .1/5 or .02 Pick a R1. Normally telemetry inputs are pretty high impedance like 100K or 1M so the divider resistance can use 1K as one of the resistances. So if R1=1K then 1k/.02 = 1K + R2 50K=1K + R2 So R2=49K. Voltage in through the 49K resistor in series with the 1K resistor then to ground. The telemetry would be fed from the junction between the two resistors and ground. From: Jesse DuPont Sent: Wednesday, August 30, 2017 11:55 AM To: [email protected] Subject: Re: [AFMUG] Cost effective battery charging and monitoring device So, R1 would be X Ohms and R2 would be X*.02 Ohms? Jesse DuPont Network Architect email: [email protected] Celerity Networks LLC Celerity Broadband LLC Like us! facebook.com/celeritynetworksllc Like us! facebook.com/celeritybroadband On 8/30/17 11:51 AM, Chuck McCown wrote: Forrest, quit working and come out and play with us.... From: Chuck McCown Sent: Wednesday, August 30, 2017 11:49 AM To: [email protected] Subject: Re: [AFMUG] Cost effective battery charging and monitoring device But you can use a voltage divider to convert the 0-5 volt to 0-.1 volt. Two resistors. From: George Skorup Sent: Wednesday, August 30, 2017 11:48 AM To: [email protected] Subject: Re: [AFMUG] Cost effective battery charging and monitoring device No, the SiteMonitor shunt input is ±100mV nominal. On 8/30/2017 12:42 PM, Jesse DuPont wrote: Would these work on a SiteMonitor? They output 1-5V DC based on current flowing through. https://flexscada.com/product/hall-effect-current-sensor-ac-75a-dc-100a/ Jesse DuPont Network Architect email: [email protected] Celerity Networks LLC Celerity Broadband LLC Like us! facebook.com/celeritynetworksllc Like us! facebook.com/celeritybroadband On 8/30/17 11:29 AM, George Skorup wrote: Yeah, about that. I wouldn't use those on 12VDC systems. Too much current. I've burned up a couple of the 10A shunts on Traco BCMUs that were running around 200W load on battery. 200/13 = 15 amps. Ungood. One site at about 225W, first time it went to battery, the shunt went kaput after 10-15 minutes and the site went down. I'm hoping Forrest comes up with some Hall effect stuff or even plain 20+ amp shunts that can be used on the SiteMonitor's existing 100mv input. Hall effect is nice because you don't have to be "in" the circuit. But I'll take what I can get. On 8/30/2017 10:26 AM, Adam Moffett wrote: Yeah, up to 10 amp. ------ Original Message ------ From: "Chuck McCown" <[email protected]> To: [email protected] Sent: 8/30/2017 11:18:36 AM Subject: Re: [AFMUG] Cost effective battery charging and monitoring device I think Forrest has them on his site with the site monitors. From: Sam Lambie Sent: Wednesday, August 30, 2017 9:15 AM To: [email protected] Subject: Re: [AFMUG] Cost effective battery charging and monitoring device Parallel. Site Monitor! Now where can I get a shunt? On Wed, Aug 30, 2017 at 9:09 AM, Chuck McCown <[email protected]> wrote: 4 batts in series or parallel? Shunt + sitemonitor would be a better way to go and you don’t have to write code. From: Sam Lambie Sent: Wednesday, August 30, 2017 9:06 AM To: [email protected] Subject: [AFMUG] Cost effective battery charging and monitoring device Hey all, I am getting away from using APC at a couple of our sites and right now I have installed a Tripp-Lite APS750 connected to 4 Deep cycle marine batteries for a total of 404 aH system. I'd like to be able to monitor the discharge rate of the batteries when power is out remotely. What have you guys been doing to that effect? I'm thinking a Pi and a shunt and some quick scripting classes on Python to put it all together... -- -- Sam Lambie Taosnet Wireless Tech. 575-758-7598 Office www.Taosnet.com -- -- Sam Lambie Taosnet Wireless Tech. 575-758-7598 Office www.Taosnet.com
