i need some more Unobtainum...

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dacflyer
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i need some more Unobtainum...

Post by dacflyer » Thu Jan 18, 2018 9:27 pm

i have a Robertshaw LP Gas Monitor model RS-228
it is a remote gas gauge if you will. the transmitter is working,, it is the receiver that is malfunctioning. i believe that it is the
RX3310A.. this chip is almost non-existent unless i order from CHINA, and wait a month or more..
i have tried to look for this a week now.. i need help.
i have even tried to buy a new unit as well, but nothing

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Janitor Tzap
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Re: i need some more Unobtainum...

Post by Janitor Tzap » Sat Jan 20, 2018 8:00 pm

Are both the sending and receiving units Battery operated?

If so......
Try replacing the batteries with fresh ones.

I've been seeing a lot of weird things with low voltage battery devices.
Even though the battery will read good with a battery tester.
If the actual voltage is just at, or a little bit bellow the running voltage of the device.
It will cause the device to act erratically.


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Re: i need some more Unobtainum...

Post by dacflyer » Mon Jan 22, 2018 4:54 am

have used fresh batteries.. no change,, the thing work and then it doesn't ..the min voltage for the unit is 2.6 V, and it uses 2 AAA batteries. the transmitter works just fine.
maybe i'll connect the display to my power supply and ramp up the voltage some and see if there is a change.
the transmitter transmits in a burst every 4 min approx..and for a duration of 2 to 4ms.
all units are battery powered.

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Re: i need some more Unobtainum...

Post by Janitor Tzap » Mon Jan 22, 2018 9:06 am

Okay,

But be careful.

Most fresh {or recharged} 1.5V Batteries will read about 1.65V to 1.68V.
Thus, the highest voltage you use with the receiver unit shouldn't go over 3.5V.

Otherwise you could fry it. :(


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Re: i need some more Unobtainum...

Post by dyarker » Mon Jan 22, 2018 9:19 am

????????????????????????????????
You replaced the receiver, still have a problem, and still say the transmitter is okay?
Or did you mean you couldn't find a new receiver to buy?

If the first case. the transmiter could be transmiting garbage.

Cheers,

P.S. A new non-rechargeable battery is 1.55V, so don't go over 3V
Dale Y

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Re: i need some more Unobtainum...

Post by haklesup » Mon Jan 22, 2018 5:50 pm

Can I assume that since the chip is an RF receiver, the display lights up but just shows an empty reading all the time?

http://www.allparts.co.kr/pdffile/pdffile_001/3274.pdf

How do you know the transmitter is transmitting or just lighting its power lamp?

Check the crystal oscillator and the series cap to the antenna, also check the antenna trace and surrounding solder joints

The part description is an "ASK receiver and searching that on google I find some on Ebay.
This module at least has a device with the same package on the board (18 lead SO)
https://www.ebay.com/i/322135571707?chn=ps

Maybe you can just find the serial data line and replace both ends of the link
https://www.ebay.com/i/231966495785?chn=ps

Finally: Here is one but in a 20 lead package.
https://www.google.com/search?biw=1324& ... 6672077689

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Re: i need some more Unobtainum...

Post by dacflyer » Tue Jan 23, 2018 5:33 am

dyarker >> no i didn't replace the receiver.. ( couldn't find a new set to buy )

haklesup>> said... Can I assume that since the chip is an RF receiver, the display lights up but just shows an empty reading all the time? CORRECT,,,

as for what i know.. the transmitter works in microsecond burst, i can see this on a "Sillyscope," so i am more than sure it is working. i see a good strong waveform.
and it transmits about every 4 min.. when it does work, the display shows info.. then after about 30 min it goes to the no signal or empty mode.
i'll put my power supply on it the next day or so,, haven't had time yet. and see what happens then..
if pinch comes to shove, i'll just repurpose the sensor ( a hall effect sensor ) and straight wire it to a new circuit..maybe something Arduino powered.. so that i can get a digital display and low fuel led and alarm or who knows what..lol

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Re: i need some more Unobtainum...

Post by dyarker » Tue Jan 23, 2018 7:06 am

... so i am more than sure it is working ...
No, you are not. You're sure it is transmitting something. Has the carrier drifted outside what the receivers are tuned for? Is the ID code transmitted the correct one for that transmitter/receiver pair? Is the data being transmitted corupt?
Dale Y

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dacflyer
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Re: i need some more Unobtainum...

Post by dacflyer » Tue Jan 23, 2018 9:52 am

i have no idea on the protocol. nor the equipment to figure that part out..
also the transmit is too short to for me to get a reading without special equipment..
but i am still pretty sure it is the receiver is the issue..

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Re: i need some more Unobtainum...

Post by haklesup » Tue Jan 23, 2018 12:17 pm

if your scope is fast enough, you should be able to lock onto the carrier frequency and check the frequency. Demodulating and reading out the digital data is more difficult but if you see modulation on the carrier, you can be relatively sure there is some kind of data. It is unlikely the data is jumbled but the carrier may have drifted so the receiver cannot tune it. Something like this could be temperature dependent. Replacing the crystal and caps on both sides should refurbish the oscillator.

Are you probing the antenna output or simulating an antenna with your probe. Often just shorting an RF diode between the probe tip and its ground will make a suitable RF probe.

In any case, I found you one, if you are relatively sure, the try will cost under a sawbuck

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Re: i need some more Unobtainum...

Post by dacflyer » Wed Jan 24, 2018 9:32 am

i probed the antenna.. the short burst i see, looks nice, but that don't tell much..
i'll mess with it more in the next day or 2 to see what i come up with..

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Re: i need some more Unobtainum...

Post by dacflyer » Thu Jan 25, 2018 4:57 am

ok,, update..
i think i got it solved.. apparently you have to keep really fresh batteries in this thing.. most stuff that runs off of 3v can still function 2.5v not this thing.. played with it a few hrs last night til it failed.
the voltage has to stay at 2.6v but the chip can operate at 5v, but i can't do that because it over drives the LCD Display. 3.2V is the max before it messes with the contrast on the screen.
so i guess what i am going to do is install a 3v Lithium battery. see how long they last compared to the 1 AA batteries.

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Re: i need some more Unobtainum...

Post by Janitor Tzap » Thu Jan 25, 2018 8:24 am

Yeah,

I kinda thought it was going to be a Battery/Voltage issue. :(

How about making a regulator circuit?
Get a LM317T and set it up for 3Vdc out, with a 9Vdc {9V Battery or 9V Walwart} Input.


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Re: i need some more Unobtainum...

Post by dacflyer » Thu Jan 25, 2018 11:28 am

ok, still playing around with this thing,, some bad design i think,, i believe that was the demise of this item, when it works it is great..
if i got super fresh batteries, it will work,, but if it gets down to 3v, it fails,, it has to be above 3.2 volts to operate...anything higher and it starts to effect the contrast of the display.

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Re: i need some more Unobtainum...

Post by haklesup » Fri Jan 26, 2018 10:47 am

LM317 is old school. and with 6V dropped across it, won't be very efficient.

there are plenty of small module battery to 3.3V regulators that will well outperform the battery in there now. Search "3V boost regulator" or similar on ebay and you'll find plenty with various specs to choose from.

Besides that, you will probably get better performance from a better alkaline battery or non rechargeable LiIon AA cell. Perhaps a Photo quality battery will sustain 3V longer before dropping off. Many battery manufacturers have discharge data to help OEM select their brand for products.

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