A really long shot.....

MikeAmann

The sensor (7518) for a Beckett Heat Manager (7812) or Intellidyne HW+ 3250 Fuel Economizer >>> has anyone ever figured out the actual IC chip number used for this sensor? The sensor is getting very hard to find (and for a reasonable price). If I knew what the chip number was, I could probably buy that for less than a buck. Or would anyone have a schematic (not a wiring diagram)?
I have a new spare sensor that I will get the numbers from tonight. The chip looks like this:


SOT-23-5 case I don't know if the chip is ANALOG or DIGITAL. Here are the Texas Instruments choices:
https://www.mouser.com/c/sensors/temperature-sensors/board-mount-temperature-sensors/?q=sot-23-5

fentonc

It's usually pretty easy if the part number is printed on it. The only tricky part would be if it's a microcontroller with firmware on it, but that's probably unlikely for a SOT-23 part.

MikeAmann

I looked into this in the past, and I think all I will find is a "house" number, meaning that the original chip number and manufacturer has been purposely hidden/obscured/removed. At least I have an unused sensor to look at.
Knowing if it was analog or digital would help me narrow it down. I'm leaning towards analog.

mattmia2

what does it sense?

MikeAmann

You ty-wrap it to your boiler's output pipe to sense the temperature.

MikeAmann

I believe I have it narrowed down to these:

mattmia2

Measure one at a couple temps if that is indeed what it is and it isn't just a thermistor in a 5 pin case.

These are a great idea for something i was trying to rig up with a thermistor.

MikeAmann

In that case, if you take this route with your project, I found this:

https://www.adafruit.com/product/1230
That "little" chip is actually half the size of a grain of rice.

ratio

If it's voltage (or resistance for that matter), it should be pretty easy to figure out what range it's looking for. Knowing that will get you directly to a compatible part.

SuperTech

With the new aquastat that you have what do you need that for? You have the same technology in the Hydrostat.

If you really one I'm pretty sure I still have the one I pulled off my boiler in my basement somewhere.

MikeAmann

All I need is the sensor. I had one die this past Saturday night. I have a spare NIB Intellidyne HW+ that I bought just for the sensor. I used that sensor last night because I installed my old Honeywell R8182D with HW+ onto my mother's boiler and it is now saving her 20%. The HW+ was saving me nearly 30% for 10+ years on my boiler.
Now I do have the Hydrostat 3250+ installed on my boiler.

MikeAmann

Before I installed the new sensor, I used a 10X eye loupe to read the only number on the chip - T8C.
And I tried to take some voltage measurements, but I was unable to get anything meaningful.
That IC is so small that the meter probes look like the size of baseball bats to a regular size chip.
I didn't want to risk damaging my now ONLY sensor, so I just went ahead and installed it.
HW+ is working great again. But now I must find a spare sensor.

MikeAmann

I FOUND IT.

https://www.aliexpress.com/item/4000041728288.html

https://en.aliradar.com/item/4000041728288-TMP05ARTZ-500RL7-marking-T8CSOT-23Board-Mount-Temperature-Sensors-IC-+-0.5-DegC-Accurate-PWM

mattmia2

I was going to say it is probably just connected to the leads and you can measure it elsewhere but you found it. I have also tack soldered little wires on to things like that to connect instrumentation to them.

MikeAmann

I have to correct the post above. It's not the TI chip. That is a 3 pin device.

The TMP05 / TMP06 is correct. https://www.analog.com/media/en/technical-documentation/data-sheets/tmp05_06.pdf

fentonc

That part is cheap and readily available: https://www.mouser.com/ProductDetail/Analog-Devices/TMP05ARTZ-500RL7?qs=WIvQP4zGanhGLsUi3oXWYQ==

SOT23 isn't awful to just hand-solder.

MikeAmann

Nice, thanks @ratio
Analog Devices is in Massachusetts.

Ok, so I can get the chip. The problem is that you have to remove the plastic casing to get to the circuit board. The plastic is cracked and deteriorated after years of heat cycles. So I can solder in a new chip, but I can't restore the plastic. What to do now?

mattmia2

I mean you can buy conformal coating in a spray can or a jar if it really needs to be there.

SuperTech

If you want mine you can have it. Just PM me your information. 

MikeAmann

@SuperTech
You missed my reply about 8 posts above. Here it is again.

All I need is the sensor. I had one die this past Saturday night. I have a spare NIB Intellidyne HW+ that I bought just for the sensor. I used that sensor last night because I installed my old Honeywell R8182D with HW+ onto my mother's boiler and it is now saving her 20%. The HW+ was saving me nearly 30% for 10+ years on my boiler.
Now I do have the Hydrostat 3250+ installed on my boiler.

HW+ is working great again. But now I must find a spare sensor.

MikeAmann

I really wish Beckett / Intellidyne used this type of sensor: https://www.google.com/search?q=clip+on+pipe+temperature+sensor&tbm=isch&ved=2ahUKEwjX64vF_5H2AhVics0KHbNdC-MQ2-cCegQIABAA&oq=clip+on+pipe+temperature+sensor&gs_lcp=CgNpbWcQAzoECAAQGFCVCVjXFGCgHmgAcAB4AIABoAKIAYcLkgEDMi02mAEAoAEBqgELZ3dzLXdpei1pbWfAAQE&sclient=img&ei=giYUYteiN-LktQazu62YDg&bih=881&biw=1280&safe=active&ssui=on
It would make things so much easier. I wish I could easily adapt one of these to the HW+.
But I have other, more important things to do.

Apparently, the earlier HM models did have a clip-on sensor: