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Topic: Smd temt6000 light sensors  (Read 2171 times) previous topic - next topic


Emitter follower AKA common collector.
Thats the name where the resistor is in the emitter.

With the resistor in the collector its called common emitter.
That gives voltage gain with an inverted output.


Jan 25, 2016, 11:24 pm Last Edit: Jan 25, 2016, 11:25 pm by Boardburner2
My setup looks like this:

That fritzing diagram is wrong , the yellow analogue lead is connected to ground not the output of the sensor.


Jan 25, 2016, 11:44 pm Last Edit: Jan 25, 2016, 11:47 pm by Marciokoko Reason: images

Thanks.  Im still learning to read schematics.  I see my mistake.  My original wiring and fritzing schematic were congruent with each but wrong because they didnt follow the order of the schematic.

So you mean like this:

What about in the breadboard, this is what I came up with:

Im not sure if it makes a difference the order within the row?  Iow, does it make a difference if I put:

A. Emitter - Signal - R
B. Emitter - R - Signal


Jan 25, 2016, 11:55 pm Last Edit: Jan 26, 2016, 12:01 am by Boardburner2
That looks correct , are you sure you understand how the rows/columns are connected in a breadboard ?

One other thing, resistors and diodes normally come with adhesive on the ends.

1/4 in should be cut off them as the adhesive will cause problems for your breadboard over time


Yes I believe I do.  Rows are all connected at every pin (1a-1b-1c-1d-1e-1f).  To connect rows I need to jump between the 2 rows I wish to connect (1a-2a = 1a-1b-1c-1d-1e-1f-2a-2b-2c-2d-2e-2f).

However my question remains as the order within each row.  I think its more a matter of not being able to visualize 3 things connected in a row.  If I see the row as a piece of wire and I plug:

1a = emitter
1b = resistor
1c = signal

how does that differ from:

1a = emitter
1b = signal
1c = resistor

As for the 1/4 inch should be cut from resistors and diodes, are you saying i should cut the tips off my resistor? 


There is no difference you had the signal wire connected to the wrong point.

cut 1/4 in , i would recommend it.
Resistors are supplied on adhesive bandoliers and can be difficult to remove.


Yes originally I did have it wrong, I understand that now.



Soooo, does it work as expected?


Would be easier to simply wire the sensor between the input and ground and use INPUT_PULLUP.


I was pondering that.
Its conceivable the sensor could be mounted some distance from the arduino, perhaps thats why the emitter follower is used.


It's not an emitter follower.

The only variable is the bias resistor.  If the INPUT_PULLUP value of around 50k is OK, then that is the way to go.  If you need a lower value, you will need to supply a pull-up resistor.

And I always refer to pull-up as if the sensor is mounted at any distance, you really do not want to connect it your V+, you want it to connect to ground and you might wish to use shielded cable.


All the examples in the vishay app notes show + connection and resistor in the emitter.

The value being between 5 K and 15 K approx, dependent on the sensitivity of the individual transistor


Jan 28, 2016, 12:30 pm Last Edit: Jan 28, 2016, 12:30 pm by Paul__B
All the examples in the vishay app notes show + connection and resistor in the emitter.
A bit like the Arduino Tutorial section eh?  Connect all your switches to +5 V.



Im still not sure why but reading the examples it may make things easier when dealing with a wide variation in component specs.


Sorry guys but I didn't get the emails alerting me to new responses!

It does work.  I'm now combining it with a led and a PIR sensor so I can have some light in my staircase at night :-)

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