using uln2803apg transistor array to activate FQP47P06 p-channel mosfet

Using Arduino General Electronics
1

I am planning to control some 5A loads (lights, pump, etc... max. 5A/each) on a car system. A brief resume of what I would like to control is:

  • 8 relay (12v) control
  • 4 lights control (5A max., each light) with the capability to fade in /fade out
  • Everything will be controlled by arduino mega
  • The main power will come from the car battery with a DC DC converter for the arduino.

I am thinking to use uln2803apg transistor arrays to control de relays. I have done some trials and it works.
I also would like to use p-channel mosfet FQP47P06 to be able to fade in / fade out the 4 lights and here is where my question is:

As p-channel gate need "0" from the arduino to switch the light on but I would like to use 5V from the arduino to activate the lights, can I just used a channel from the uln2803apg transistor to do so? (see attached diagram)
The reason to do that is to avoid having the lights momentary on every time the arduino is started.

Skech.PNG
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2

You have GND on either side of the load.

Skech.PNG
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3

Reasonable the 2803 would work as below.

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See Q5

Outputs.jpg
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4

wow!! what I mistake!!!

Thanks for the quick reply!

I have updated, and attached, my diagram ......

Will I need a resistor between the transistor array )uln2803apg) and the p-channel mosfet (FQP47P06) or not rally neccesary?

Skech2.PNG

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cb54f86922970874134ece226ae2de3a4143f4c8.png

6

irrintxi:
I am thinking to use uln2803apg transistor arrays to control de relays. I have done some trials and it works.

Mega seems overkill.
I would use something like a TIP6B595 shift register that can switch eight relays directly.
Uses only three Arduino pins, and you can add more chips/relays that use the same three pins.
That chip could also drive P-channel fets.
Leo..

7

Will I need a resistor between the transistor array )uln2803apg) and the p-channel mosfet (FQP47P06) or not rally neccesary?

As you have it now, it would work.

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8

larryd:
As you have it now, it would work.

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I mean a resistor between the transistor array and the p-channel gate.

9

No.

10

Wawa:
Mega seems overkill.
I would use something like a TIP6B595 shift register that can switch eight relays directly.
Uses only three Arduino pins, and you can add more chips/relays that use the same three pins.
That chip could also drive P-channel fets.
Leo..

I will have a look at it. I have so much to lern......

Why do you think the mega will be overkill? Each pin from the arduino should not have more than 20ma for echa relay to be activated (using the uln2803apg).

11

larryd:
No.

Unless you're expecting spikes >25volt on your 12volt (car) supply.
Then a (~18volt) zener diode between 12volt and gate could be wise.
And maybe a (220ohm) CL resistor for that zener and chip between gate and transistor array.
Leo..

12

irrintxi:
Each pin from the arduino should not have more than 20ma for echa relay to be activated (using the uln2803apg).

The Arduino only provides signal current to the ULN transistor array.
About 1.5mA per channel.
Leo..

13

Wawa:
Unless you're expecting spikes >25volt on your 12volt (car) supply.
Then a (~18volt) zener diode between 12volt and gate could be wise.
And maybe a (220ohm) CL resistor for that zener and chip between gate and transistor array.
Leo..

Not really expecting those peaks!

Thanks!

14

Wawa:
The Arduino only provides signal current to the ULN transistor array.
About 1.5mA per channel.
Leo..

The the arduino mega shouldn't "sweat" for my aplication, isn´t it?

This is the idea:

sketch3.png
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15

Note on the previous diagram, the relays reference are not right. On the diagram, the refefrence corresponds for 3v powered but I will change then for 12v ones (Same size).

Will the 1K resistor, between p-channel mosfet and 12v, be ok? Is it a right value?

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