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Topic: Cheap and good way to feed 12v digital input (Read 11653 times) previous topic - next topic

Grumpy_Mike

Quote
Actually I am not using it to trigger any arduino pin..

So what are you using it for?

dlloyd

Cheap, good and small:
SOT-89 (7805): 1.6mm x 4.6mm, area 7.36mm2,
SOT-416 (DTC114W): 1.7mm x 0.9mm, area 1.53mm2, $0.20 each
I/O Connections: VIN 0-30V, OUT (inverted) connected to PIC input with Pull-up enabled.

Joy


Quote
Actually I am not using it to trigger any arduino pin..

So what are you using it for?


I have mentioned it on my previous post. I am actually using it to trigger a SMD 8 Pin PIC Microcontoller..

The main target is to make the PCB as tiny as possible and making it cheap retaining the quality, as it will be mass produced..

Joy


Cheap, good and small:
SOT-89 (7805): 1.6mm x 4.6mm, area 7.36mm2,
SOT-416 (DTC114W): 1.7mm x 0.9mm, area 1.53mm2, $0.20 each
I/O Connections: VIN 0-30V, OUT (inverted) connected to PIC input with Pull-up enabled.


I am unable to make out how will it work..
I went through the datasheet too, bu cant make out..It would be kind of you, if you can elaborate please..

dlloyd

Hint:
The 7805 has 3 terminals (INPUT, OUTPUT, GND).
The DTC114W has 3 terminals (IN, OUT, GND).

Grumpy_Mike

Quote
I am actually using it to trigger a SMD 8 Pin PIC Microcontoller..

What does that mean?
By trigger do you mean turn on, like applying power controlled by something else?

That sounds like an even worse idea.

rmetzner49

It's actually quite novel.  He connects the GND to ground, obviously, the OUT to the input pin on his Arduino, and the IN of the regulator to his switch or whatever his 12V signal is.  The 7805's output will be 5V with anything from about 7V to 30V on its input.

Not how the manufacturer envisioned its use, but should work just fine.

dlloyd

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Not how the manufacturer envisioned its use, but should work just fine.


Hmm...no capacitors.

Here's what the Society of Robots has to say about that.

JimboZA


Here's what the Society of Robots has to say about that.


Bit misleading: It's no more the Society of Robots saying anything than Messrs Arduino saying anything in this public forum, is it? (However correct the individual member's views may be....)

That said, not one of the many schematics in the 7805 datasheet lacks caps.
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Your answer may already be here: https://forum.arduino.cc/index.php?topic=384198.0

cjdelphi

The caps would be very bad for serial communication... the 7805 will work up to a certain frequency but then it simply can't switch between 0 and 5v fast enough killing the serial data...

Change the 2 zener resistors for 10k to keep the current down.


CrossRoads

So what's the argument against using simple resistor divider with a zener just in case the input exceeds 16V?
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

dlloyd

Quote
I am unable to make out how will it work..
I went through the datasheet too, bu cant make out..It would be kind of you, if you can elaborate please..


Just 2 parts, smaller footprint, low cost 5.5ยข per PCB (qty 1000)
High performance: 0-30V Input, Max 250MHz transistor frequency, Inverted 0-5V output

DTC114W Digi-Key $0.04844 each (qty 1000)
ERJ-2RKF2201X Digi-Key $0.00699 each (qty 1000)


Joy


Quote
I am actually using it to trigger a SMD 8 Pin PIC Microcontoller..

What does that mean?
By trigger do you mean turn on, like applying power controlled by something else?

That sounds like an even worse idea.


I actually meant that I am giving just and ON / OFF signal to the digital input of a PIC and the controls a condition..
I ON / OFF switching is not at all fast..

Joy


So what's the argument against using simple resistor divider with a zener just in case the input exceeds 16V?


There is no argument at all..

The issue is the space in the PCB. I have to fit components in a very tiny place, so lesser components, easier for me..

CrossRoads

Two 0402 resistors and an 0603 zener, that's pretty small.
What quantities are you making these in?
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

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