I love watching Limor/Lady Ada take apart a Consumer Electronic device and explain to us what the chips are and what is going on.  I thought what a great learning opportunity to take something that I have some familiarity with – in this case pH and EC circuits – and find a product to take apart and figure out how the circuit works. 

pH/EC-983

The product I picked was the ph/EC-983.  I picked up a couple on eBay.

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This handy tool integrates a pH and EC probe as well as gives a temperature reading.  It is inexpensive and if it is “good enough” I was thinking it would be super amazing to plunk the probe in the nutrient bath.  I would use firmware to take pH/EC measurements and use the measurements to adjust the pH and nutrients.

I was mostly interested in the bottom piece.  The bottom piece contains the pH and EC probes:

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I was thinking if I could figure out the signals coming out of the probe:

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So that I could put the probe in the nutrient bath and connect up a pH/EC circuit to be monitored through firmware.

 Hmmm…I couldn’t pry apart the device in the nice, clean way Lady Ada is able to…so…out came the Dremel!  

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The Active Parts

To get started, I looked at the active parts.

These two images show the location of the parts:

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HEF 4053BT

Two of the chips are the HEF 4053BT (data sheet):

HEF4053BT

From the data sheet: The HEF4053B is a triple single-pole double-throw (SPDT) analog switch, suitable for use as an analog or digital multiplexer/demultiplexer.   This page on Basic Electricity has a great discussion on switches including SPDT switches.

HEF 4011BT

Another is the HEF 4011BT (data sheet):

HEF4011BT

From the data sheet: The HEF4011B is a quad 2-input NAND gate.

062C

Another chip is a variant on the 062C dual op amp (data sheet):

062C DualOpAmp

ICL7106

The internal ICL7106 (data sheet):

ICL7106

From the data sheet: TheICL7106 is designed to interface with a liquid crystal display(LCD)…

HEF4030BT

Unfortunately, I got a little too aggressive with the Dremel.  I’m still able to make out this chip is a HEF4030BT (data sheet):

HEF4030B

From the data sheet: The HEF4030B is a quad 2-input EXCLUSIVE-OR gate. 

Maxim ?

Drat…the Dremel scratched the markings off this chip.  I can tell it is a Maxim and there looks to be A1601…or A1801…or…:

MaximTBD

SGM3005 XMS

The SGM3005 XMS (data sheet): 

SGM3005XMS

From the data sheet: The SGM3005 is a dual, low on-resistance, low voltage, bidirectional, single-pole/double-throw (SPDT) CMOS analog switch designed to operate from a single 1.8V to 5.5V power supply.

At this point, my eyes hurt.  Time to stop for now.

 

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