Cheap and good way to feed 12v digital input

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.

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.

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.

dlloyd:
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.

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.

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

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 5.5¢ 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)

Grumpy_Mike:

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..

CrossRoads:
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..

Two 0402 resistors and an 0603 zener, that's pretty small.
What quantities are you making these in?

CrossRoads:
Two 0402 resistors and an 0603 zener, that's pretty small.
What quantities are you making these in?

yes I know, that these 3 components are really small.. But 3 different footprints will require lil more space.. And the 7805 SOT-89 package is taking lesser space..

Making them in 1000+ quantities.. on homemade PCBs. So will not be able to make very thin tracks... If I could then would have been able to fit the two 0402 resistor and a 0603 zenner in a very tiny space..

dlloyd:

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 5.5¢ 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)

Will this work too..??

1000+ & homemade PCBs? You are a glutton for punishment!

mmun2215 - I don't see why not.

CrossRoads:
1000+ & homemade PCBs? You are a glutton for punishment!

hahaha..

please don't get me wrong..

The reason I use the homemade PCB is that there is no good estimation that how many will sell off..
Hence the keep making these 50 - 70 at a time..
It just takes half an hour to make the PCB...

And profit margins form the product is very very low..

CrossRoads:
mmun2215 - I don't see why not.

I did not get this Sir..:open_mouth:

What's with the second resistor on the npn's base? (pull down? It's not a fet, it's not biasing?)

Ahh my bad... resistor divider!

Will this work too..??
http://in.element14.com/on-semiconductor/mmun2215lt1g/transistor-digital-sot-23/dp/9556680?whydiditmatch=rel_3&matchedProduct=dtc114&matchedProduct=dtc114&whydiditmatch=rel_3

Yes, this type will also work.

Note that the transistor begins to turn at about VBE = 0.5V.
The MUN2215 will turn on when the input is at 0.5V.
The DTC114W will turn on when the input is at 1.5V, providing higher noise immunity.