ok,, New Project time,,,

This is the place for any magazine-related discussions that don't fit in any of the column discussion boards below.
User avatar
dacflyer
Posts: 4439
Joined: Fri Feb 08, 2002 1:01 am
Location: USA / North Carolina / Fayetteville
Contact:

ok,, New Project time,,,

Post by dacflyer » Tue Dec 04, 2018 7:41 pm

ok, My old ROBERT SHAW RS-228 Propane monitor went belly up.
https://www.bakersgas.com/rs228.html
ROBRS228.jpg
ROBRS228.jpg (10.43 KiB) Viewed 3762 times
i have kept this thing limping along as long as i could. but it is no more, and there is nothing on the market that is a stand alone device with a display.. there is wifi and BT devices out there, but all i wanna do is just look up and see a simple display that tells me the % of fuel.. i have a 100 gallon tank, it has the remote ready sensor on it.
http://www.rochestergauges.com/products/R3D-LP.html
lp guage.jpg
the specs of the hall sensor are....
Opp. Range 4.5 to 5.5 vdc/ratiometric.
Can be made compliant with alternative operating voltages.
Output Voltage with 5.0 Volt Input
Ratiometric 8-80% of input voltage @ 8-80% volume.
Ratiometric: Empty is 0.4 volt or 8% of input voltage.
Full is 4.0 volt or 80% of input voltage

I'd like to make me a display 2 digit 00-99 led display and i think i need the reading range to be like ( Empty = 0.4V =8 %? and Full = 4V = 80% ) according to the specs ? i think this may require a micro controller.. but i could probably be happy with the the old school LM3914 display.
just have to have advice on both. the LM3914 i can do, i just need to figure out how set it up for the particular range.. 0.5V min and 4V max ?
not sure how to calculate that.
if i do the code, i'd have to have someone write the code. i can only assemble.. an Arduino nano and an Adafruit display sounds easiest.

comments advice ?

User avatar
Janitor Tzap
Posts: 1434
Joined: Sat Aug 12, 2006 5:17 pm
Contact:

Re: ok,, New Project time,,,

Post by Janitor Tzap » Wed Dec 05, 2018 9:31 pm

Dacflyer,

So your still looking for a replacement for your old propane monitor.

I came across this one on youtube.
https://www.youtube.com/watch?v=4PTJ1KajJrc

This is the company that makes it.
https://mopeka.com/


Signed: Janitor Tzap

User avatar
haklesup
Posts: 2955
Joined: Thu Aug 01, 2002 1:01 am
Location: San Jose CA
Contact:

Re: ok,, New Project time,,,

Post by haklesup » Thu Dec 06, 2018 11:31 am

Since you have access to a proportional voltage, the hard part is done.

If you want Old School then get a mechanical ammeter movement, figure out the resistor network to get the needle to deflect full scale at 4V and replace the graphics behind the needle with a custom scale 0 to 100%. (assuming it has enough current at 4V, you didn't comment on that)

While you already have a mechanical needle display, Can I presume you want this to be remote and wired?

Maybe you really want digital, the divide the voltage by 4 so you have 1V Full scale and just use a voltmeter and pretend millivolts are percents

User avatar
dacflyer
Posts: 4439
Joined: Fri Feb 08, 2002 1:01 am
Location: USA / North Carolina / Fayetteville
Contact:

Re: ok,, New Project time,,,

Post by dacflyer » Mon Dec 10, 2018 12:16 pm

Janitor >> i don't want a wifi type or App type monitor.
i think i decided on using the LM3914 it'll be easier than a analog meter pointer from across the room.
i just need some figuring out done for me ( horrible at math ) i need to know what the voltage divider resisters need to be for a 4v or 5v full scale
i think this will be easiest.

i do also have now a CA3161 & CA3162 2 digit meter.. found them in my junk box,, they are out of some old C-Band dish movers.
so same thing i guess, if i can figure out the voltage dividers ( if someone is kind enough to help me out ) then i can make either display i choose..
the digital one would just be 00-99 range, but close enough for my needs, as a propane tank is usually considered full at 80% or so.
they usually can put in a bit more if it's going to be cold for a while.

either one i choose will be direct wired. no radios.

User avatar
Janitor Tzap
Posts: 1434
Joined: Sat Aug 12, 2006 5:17 pm
Contact:

Re: ok,, New Project time,,,

Post by Janitor Tzap » Mon Dec 10, 2018 5:26 pm

Sorry......

When I had looked at the video, the guy didn't say that it was Blu-Tooth. :(
Also, after going out too the Mopkea website and looking at the spec's of the unit.
The sender units only can be used with tanks as large as 30 gallon. :(

Here's the Ohms Law Calculator for Voltage Dividers.
http://www.ohmslawcalculator.com/voltag ... calculator


Signed: Janitor Tzap

User avatar
dacflyer
Posts: 4439
Joined: Fri Feb 08, 2002 1:01 am
Location: USA / North Carolina / Fayetteville
Contact:

Re: ok,, New Project time,,,

Post by dacflyer » Tue Dec 11, 2018 7:56 am

i looked at that ohms law calculator.
problem is, i don't know what value resistors i need.. i only know the input voltage. and not sure about the output voltage.. is that even prudent to my project ?

User avatar
Lenp
Posts: 1390
Joined: Thu Oct 26, 2006 8:11 pm
Location: Maryland
Contact:

Re: ok,, New Project time,,,

Post by Lenp » Tue Dec 11, 2018 11:29 am

When the math fails, resort to emperical observation, roughly translated - get a potentiometer and just diddle with it to see what works best! :grin:
Len

“To invent, you need a good imagination and a big pile of junk.” (T. Edison)
"I must be on the way to success since I already have the junk". (Me)

User avatar
dacflyer
Posts: 4439
Joined: Fri Feb 08, 2002 1:01 am
Location: USA / North Carolina / Fayetteville
Contact:

Re: ok,, New Project time,,,

Post by dacflyer » Tue Dec 11, 2018 2:55 pm

i guess i could try that.. will i need 2 pots or just 1 ? i am thinking 2 of them..

User avatar
Lenp
Posts: 1390
Joined: Thu Oct 26, 2006 8:11 pm
Location: Maryland
Contact:

Re: ok,, New Project time,,,

Post by Lenp » Tue Dec 11, 2018 5:32 pm

One pot....
One end to the source
One end to common
Center to the input
It's a classic voltage divider
Len

“To invent, you need a good imagination and a big pile of junk.” (T. Edison)
"I must be on the way to success since I already have the junk". (Me)

User avatar
dacflyer
Posts: 4439
Joined: Fri Feb 08, 2002 1:01 am
Location: USA / North Carolina / Fayetteville
Contact:

Re: ok,, New Project time,,,

Post by dacflyer » Tue Dec 11, 2018 7:34 pm

oh, ok, so it does not have to be balanced on both ends.. ok,,
so 2 resistors = the total of a pot, and the wiper moves to my needed value..
ok,, sounds really easy now..
i'll give it a punt and let ya'll know later on.

User avatar
dacflyer
Posts: 4439
Joined: Fri Feb 08, 2002 1:01 am
Location: USA / North Carolina / Fayetteville
Contact:

Re: ok,, New Project time,,,

Post by dacflyer » Sun Dec 16, 2018 6:47 pm

i've tried to figure this volt meter thing out, i just can't get the input configuration right.
i know it is old school technology, but it's got me whipped.
the IC in question for me is the CA3162
the voltage i want to measure is from 0-5v approx. ( .8- 4v specific ) but with adjustments, i should be able to tweak it.
i ditched the LM3914 idea,, i decided i wanted a digital readout instead.

User avatar
Lenp
Posts: 1390
Joined: Thu Oct 26, 2006 8:11 pm
Location: Maryland
Contact:

Re: ok,, New Project time,,,

Post by Lenp » Sun Dec 16, 2018 7:48 pm

What is the value of the pot you tried. If it is too low it may load the sensor voltage and it will go too low. Off the cuff, I would try a 10-100 k pot(linear) preferred
Len

“To invent, you need a good imagination and a big pile of junk.” (T. Edison)
"I must be on the way to success since I already have the junk". (Me)

User avatar
dacflyer
Posts: 4439
Joined: Fri Feb 08, 2002 1:01 am
Location: USA / North Carolina / Fayetteville
Contact:

Re: ok,, New Project time,,,

Post by dacflyer » Tue Dec 18, 2018 11:34 am

i tried 1K , 10k , 50k , 100K it's too sensitive either too high or too low.. there's gotta be something more to the circuit i'm missing..
it has to be related to the input pins 10, 11 of the CA3162 iC

and what is the function of the GAIN control of pin 13
i know this should be something simple,, but it's got me stumped.
i know it'll be a DOH!!!! moment later on.

User avatar
haklesup
Posts: 2955
Joined: Thu Aug 01, 2002 1:01 am
Location: San Jose CA
Contact:

Re: ok,, New Project time,,,

Post by haklesup » Tue Dec 18, 2018 12:03 pm

Here is the datasheet, its a bit old school and doesn't contain many application examples.
http://pdf.datasheetcatalog.com/datashe ... fn1080.pdf

The high and low inputs are pretty much a differential amp input high impedance. I suppose you could ground the neg imput and operate it single ended in which case making a voltage divider with the high pin at the middle and the sensor voltage at the top (bottom grounded) should be easy to get a set of solutions for 1/4 scaling of the voltage, use relatively high values to keep the load current low and not over load the sensor source.

It can operate in differential mode that's more useful for measuring current but you could measure voltage with floating ground for example.

The gain changes the mV per V sensed at the input, unused the DS says set to 900mV. I suppose that's a way to scale up small voltages to match the display range. The zero offset can be used to correct for the 400mV when empty.

So I suggest you ground the low input and build a 2 resistor divider and then use the gain and offset to dial in the range for the sensor you are using.

User avatar
dacflyer
Posts: 4439
Joined: Fri Feb 08, 2002 1:01 am
Location: USA / North Carolina / Fayetteville
Contact:

Re: ok,, New Project time,,,

Post by dacflyer » Tue Jan 29, 2019 3:44 pm

ok,, so i messed around with this a bit more..
i don't think my sensor is gonna work with this set up.
the sensor seems to max out at 4.08V which is about 75% of my sensor.
so i don't know what else to do.. so from about 75% - 85% ( considered a full tank ) there is no change in readings. And there is no way that i know of to compensate. the readings are kinda accurate down to 50% , but then start to drift fast twards empty ( 8% is considered empty )
lowest readings are close to 0V, but it will go down to Mv. readings.
i could live with the full down to 75% readings for full. but i think i might need a micro to get accurate readings on down to empty..
i need some other suggestions.
this is a link to a similar circuit i used.. may not be right..
http://www.circuitstoday.com/digital-t ... er-circuit

i'd like something like this, but Damn the price.. how do they justify the price
https://fuelminder.biz/lpg%20gauge/lpg% ... 0info.html

Post Reply

Who is online

Users browsing this forum: Bing [Bot] and 9 guests