Deconstructing the Sure Temperature Sensor

[Driver+Passengers]

Carrying on from the side-project started some way through the thread "DIY non invasive temperature gauge probe placement ideas...", this thread will hopefully see out the investigations into how one might add an alarm feature.

The units under consideration are in the range ME-SP330 to ME-SP335.

tallbongo has been looking at a hardware solution to add an alarm based on the resistance of the NTC thermistor probes. I'm looking into how the existing software/circuitry might be modified to support it.

Here goes...

(This is all assuming that the unit will stay in production long enough for all this work to bear fruit... )

[bikerbob]

I`m considering buying another unit from Sure as you say they may withdraw it from production but will ask for them to check sensors & channels calibration, for just £9.00 its worth having a spare as I find it a useful addition to engine monitoring, will also be buying one of Haydns low coolant alarms for a belt & braces approach to engine monitoring.
Good luck guys and will leave this link for you techs, unless of course I have something intelligent to say

[Driver+Passengers]

Cheers, Bob. Your old unit arrived with me this morning, so I now have something to test with.

A 4.7K resistor between GND and CH1 gives a reading of 46.1°C. With another 1K in parallel (reduces resistance, should increase temperature), the reading becomes -22°C. So I can confirm that this unit is 'borked' - and given what the manufacturer claims, it's a software fault for which I have the revised code that was sent to Bob.

I've soldered an ICSP header to J4 on "Bob's unit" (as it will henceforth be known) and the back still fits on. This header also exposes pins 10 and 12 - RB7/TX and RB5/RX respectively.

I shall make up a cable and resurrect the PIC programmer to try out the .hex file Bob sent me. I may work on the schematic over the weekend.

I can also confirm that this unit (and the code I've been looking at) does not support the DS18B20s. Yet...

[Driver+Passengers]

I'm going to bed - this is getting way out of hand!



Can someone check this for me...

[The_Gordons]

It's been a while since I programmed a PIC but I made up a simple temperature logger that I was going to use in a greenhouse using a PIC and a Dallas one wire device. The circuit was quite simple and worked well. I used a cheap alphanumeric LCD display as it allowed me to display current temperature along with minimum and maximum temperatures. Add on a LCD graphical display and you could wasily have a rolling graphical plot of temperature.

[Driver+Passengers]

It's been a while since I programmed a PIC but I made up a simple temperature logger that I was going to use in a greenhouse using a PIC and a Dallas one wire device. The circuit was quite simple and worked well. I used a cheap alphanumeric LCD display as it allowed me to display current temperature along with minimum and maximum temperatures. Add on a LCD graphical display and you could wasily have a rolling graphical plot of temperature.

Very cool - it's really satisfying when you get something like that working. I'm doing just that over here... viewtopic.php?f=3&t=51575. I've just taken delivery of a 240x128 blue backlit LCD. SD card socket in the post.

[Driver+Passengers]

By disabling two of the dip switches, I can free up an I/O pin (have to check it can be made to output). Can use the switch contacts to solder on to - they're large enough. Also, the MCLR pin might be available for use.

There are three timers on the chip, two of which are used. So TMR1 is available to use to vary the beep patterns. A single momentary switch could be used to alter the alarm temperature.

There should easily be enough code space to do this. 1-wire is on hold for the moment.

[Driver+Passengers]

I shall make up a cable and resurrect the PIC programmer to try out the .hex file Bob sent me.

New hex file works, now reading something like 108°C, where I used to get -22°C.

Anyone who has a 'duff' unit and wants the software upgraded I will do this FoC if you send your unit with an SAE. Feel free to PM. That said, you may want to wait until I can do the buzzer mod at the same time, and perhaps calibrate, if I can work out how.

[bikerbob]

look forward to the buzzer & calibration mod to apply to my new unit,

[Driver+Passengers]

look forward to the buzzer & calibration mod to apply to my new unit,

Volontiers!

[Driver+Passengers]

By disabling two of the dip switches, I can free up an I/O pin (have to check it can be made to output). Can use the switch contacts to solder on to - they're large enough.

Having had a flick of the switches, I've determined the following:

3:off 4:off - just CH2 temp
3:on 4:off - just CH1 temp
3:off 4:on - "CH1" / "CH2" and temps
3:on 4:on - like above, but repeats the same channel it was on when switched

1:off 2:off - display in degC
1:on or 2:on - display in degF
1:on 2:on - the display freezes at whatever it was on

Also, in "CH1"/"CH2" degF, the display flickers when displaying "CH2".

So basically you can't have 1/2 on together, nor 3/4 together.


Whatever - I only need to know that I'm going to disconnect switches 1 and 2 to use the pin as an output to driver the buzzer, and hard code it in software to always display degC.

[jaylee]

Occasionally "CH1"/"CH2" the display flickers when displaying in C too... I thought it may have had something to do with rapid temp change? Or a kind of "hold on i'm in the middle of weighing this temperature up" sort of thing?

I have a PDF with the instructions... No mention of the flashing C or F!! That sort of flash on a digital temp read out tends to happen when below zero on other gauges of this sort..!? (My old Vauxhall.) But this don't happen in conjunction with a - symbol on the sure gauge.

[Driver+Passengers]

Occasionally "CH1"/"CH2" the display flickers when displaying in C too... I thought it may have had something to do with rapid temp change? Or a kind of "hold on i'm in the middle of weighing this temperature up" sort of thing?

I have a PDF with the instructions... No mention of the flashing C or F!! That sort of flash on a digital temp read out tends to happen when below zero on other gauges of this sort..!? (My old Vauxhall.) But this don't happen in conjunction with a - symbol on the sure gauge.

Instructions?!? Would you be able to forward me a copy of that, for reference... not because I need it...

Interesting re: the flicker... I may be tempted to track it down eventually, but I really should just be recoding this thing from scratch in C, not reverse engineering the assembly!! Again,

[Driver+Passengers]

...I'm going to disconnect switches 1 and 2 to use the pin as an output to driver the buzzer, and hard code it in software to always display degC.

I've now permanently disabled SW1/2 on Bob's unit by removing resistors R23, R27 and R28, and fudged the ADC return value for AN11 (pin 12) to 0x3:0xFF (to simulate pull-up to 5V with both switches 1 and 2 open).

Fine so far. Next, I want to run the output from the PIC through a resistor to an NPN transistor, emitter to ground, collector via buzzer to 12V - for the volume. Though there is (just) enough space in the back of the unit to fit the mini-buzzer I've got, I may drill a hole in the back cover and have it poking out a mil' or two, just to get maximum sound pressure out of the unit.

[jaylee]

Occasionally "CH1"/"CH2" the display flickers when displaying in C too... I thought it may have had something to do with rapid temp change? Or a kind of "hold on i'm in the middle of weighing this temperature up" sort of thing?

I have a PDF with the instructions... No mention of the flashing C or F!! That sort of flash on a digital temp read out tends to happen when below zero on other gauges of this sort..!? (My old Vauxhall.) But this don't happen in conjunction with a - symbol on the sure gauge.

Instructions?!? Would you be able to forward me a copy of that, for reference... not because I need it...

Interesting re: the flicker... I may be tempted to track it down eventually, but I really should just be recoding this thing from scratch in C, not reverse engineering the assembly!! Again,

Rhino-wayne found & posted it up on the "other thread"... http://www.sure-electronics.net/downloa ... 1.0_EN.pdf