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Topic: Beginer : Transistor NOT gate? (Solved) (Read 1 time) previous topic - next topic

empereuri

Sep 27, 2017, 06:26 am Last Edit: Sep 27, 2017, 06:46 pm by empereuri
Hi all, just bought arduino starter kit and started a projet to autonomously water my plants.

i thought of a way to do it, but to be efficient, I would need to turn a switch OFF when the input is Hi. I have seen a few turorial on how to do that by causing a shunt, but in my circuit there would be a lot of that, and i'm worry about taking to much of current juste to switch on off a few thing.

So here is my question... is there is any transistor that switch off when imput is hi? witout needing to shorting anything and without using an inverter???

Any help would be apreciated as I've been googling about this for a few hour now!

thanks!

Fran├žois

kenwood120s

#1
Sep 27, 2017, 06:41 am Last Edit: Sep 27, 2017, 06:55 am by kenwood120s
Since you're talking about using an Arduino, by far the easiest way to get things working one way or the other is in your code's logic.

It's trivially simple to read a sensor and output a high on another pin if the sensor's low. It's just as simple to output a low if the sensor's low. You can even change your mind next week if you like, and flip the logic in your code without needing to mess with the hardware.

[gumby]I've got my head stuck in the cupboard[/gumby]

Noobian

You could also achieve this with a relay module.

edgemoron

What is the voltage on the sw? How much current through the sw? Can you post a diagram?
HowToPost


empereuri

#4
Sep 27, 2017, 10:18 am Last Edit: Sep 27, 2017, 11:18 am by empereuri
It's trivially simple to read a sensor and output a high on another pin if the sensor's low. It's just as simple to output a low if the sensor's low. You can even change your mind next week if you like, and flip the logic in your code without needing to mess with the hardware.
Yes that is thrue, the probleme with that is that since i'm planing to controle quite a few servo motor, I think i'm going to lack of output. so insted of two pin for each iteration (see graph) i would only need one with a "off" transistor...

You could also achieve this with a relay module.
I'll google that right away! thanks for the advice!

What is the voltage on the sw? How much current through the sw? Can you post a diagram?
HowToPost


O__o i guess i'm really newb.... but i don't understant the question, what is sw?

Basicly, i will have to control like 16 servo motor (but only one at once), and i'm planning to had input from moisture sensor (like 16 of teem) so the number of pin used is limited.

So i was planing to make a iteration of switch to have only one motor powered at a specific time. wich imply using quite a few transistor. For each "iteration" i need some switch on and some switch off. If i take kenwwood advice, for 12 motor, i'll need 10 pin instead of 5. But i'f i use inverter or other trick to make a Transistor NOT gate, with like more then 20 transistor i'm afrain to draw to much current...
the only source of power is the arduino itself



i did the schema with only 8 servo motor, for 12 i will have to had an "iteration". every transistor with reverse sign are the one i would like to turn off when at HI

thanks all for your time!

MarkT

Hi all, just bought arduino starter kit and started a projet to autonomously water my plants.

i thought of a way to do it, but to be efficient, I would need to turn a switch OFF when the input is Hi. I have seen a few turorial on how to do that by causing a shunt, but in my circuit there would be a lot of that, and i'm worry about taking to much of current juste to switch on off a few thing.

So here is my question... is there is any transistor that switch off when imput is hi? witout needing to shorting anything and without using an inverter???

Any help would be apreciated as I've been googling about this for a few hour now!

thanks!

Fran├žois
High side switch with a PNP BJT or p-channel FET will do this.
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]

empereuri

You could also achieve this with a relay module.
Ok just googled that and yes, that's exactly what i need... I guess the realy really acte as a "transistor" but with the possibility to have it normaly on or off.... Thanks a lot! really helpfull

High side switch with a PNP BJT or p-channel FET will do this.
I'll will take a look at that, but i think i already look at that (not totally sure if it's the same terminologie)
but i think that of each signal i turn to off, i will have to pass a bit un diverted current  and with like 20 of those, i don't think the arduino uno can take it (I can be totally wrong!)

MarkT

Ok just googled that and yes, that's exactly what i need... I guess the realy really acte as a "transistor" but with the possibility to have it normaly on or off.... Thanks a lot! really helpfull
What is the load you are switching?

Why do you need HIGH to mean off?
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]

empereuri

#8
Sep 27, 2017, 11:23 am Last Edit: Sep 27, 2017, 11:33 am by empereuri
What is the load you are switching?

Why do you need HIGH to mean off?
The load i need to switch is the power to the servo-motor (5V) (only one will be powered at one given time), sorry the schema did not load up, i redid it and it should be avalaible on my last post (but i'll had it here juste in case)

I need HIGH to mean off to avoid using more pin on the arduino. i do a serie of on/off, to be able to controle multiple servo with minimal pin use...

empereuri

I won't reply for a few hour, as it's 5h30 am, i think it's time to sleep a bit! thanks all for your input/comment

edgemoron

#10
Sep 27, 2017, 04:05 pm Last Edit: Sep 27, 2017, 04:05 pm by edgemoron
Please describe the component in the green box. :)

kenwood120s

Please describe the component in the green box. :)
It's like the scene from one of the Rambo movies:

What's this?
A blue light.
What's it do?
Turns blue.

[gumby]I've got my head stuck in the cupboard[/gumby]

edgemoron


empereuri

Please describe the component in the green box. :)

haha! well, i think we can all conclude that this is not the best drawing! It's just a normal transistor (but i draw the wire first O__o)

I sleep on that... I think, in then end, the best thing would be to have a 10 pin inverter... But if it invert the singnal of 5 pine at the same time... will it draw to much power from the arduino to the point to prevent a servo motor to do is job?

aarg

It's just a normal transistor
Then you are both drawing too much current from the Arduino and overdriving the transistor.
  ... with a transistor and a large sum of money to spend ...
Please don't PM me with technical questions. Post them in the forum.

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