Step Ups and the Arduino?

Development Boards Arduino
1

I’ve done a few simple projects w/ Arduino, but am still a noob, so please keep your responses at the ‘elementary’ level :pray:

I’m trying to use my arduino to control things that are DC powered, and beyond the power capabilities of the arduino - namely, I have a 12v fan, 12v LED light strip, and a 6-8v robot motor. So I’ll need 30-32v in total. I know the arduino can only dish out about 5v (correct?).

So my question is, short of running a separate power supply to each device and using relays, how would you use the arduino to turn the fan and led strip on and off (and they could be on for an extended period of time) while also controlling the motor in bursts of 6-8v?

2

12v fan, 12v LED light strip, and a 6-8v robot motor. So I’ll need 30-32v in total.

Doesn’t work like that with voltage. You take your highest voltage device, 12V, and that’s what you need.

The current is another story. Those you add up. 100mA fan + 1A strip + 200mA motor = 1300mA or 1.3A (these are guesses since you didn’t post any specs or details)

3

jdlev:
short of running a separate power supply to each device and using relays, how would you use the arduino to turn the fan and led strip on and off

That’s pretty much exactly how I’d do it.

4

Sorry…I’m still learning, and electrical things have been a bit of a black art to me. Looks like this is going to require a lot more components than I thought.

I’ve heard a few analogies of elctricity to water. So voltage would be the diameter of the water pipe, amps would be the rate that the water would flow at…let’s say gallons per minute, and the wattage would be the total amount of water to flow through the pipe. Maybe I’m thinking about this project wrong, and should be thinking step down from a single device as opposed to a step up from the arduino.

So let’s start at the power supply. AC. The AC naturally has to be broken down to DC which will require a transformer. Couple questions:

  1. Would it be better to have one large transformer that takes the AC and converts it to straight DC, or should I go with 3 smaller transformers that only draw the required voltage according to each device?

  2. The smaller transformers (like something you’d use to power a cell phone) will take up more space, but I’m guessing I wouldn’t have to use any type of diodes, capacitors, or rectifiers with them would I?

  3. Could I get by with just 2 transformers? One that provides enough amperage to both the 12v devices, and one that has a 6v rating? Or better yet, could I just get 1 12v tranformer, and then have one that provides enough amperage to power all 3 devices with some sort of voltage step down between the device that requires 6-8v…like a voltmeter? Something like this ac to dc converter that supplies 12v at 5.8 amps looks like it could handle the job pretty easily…what do you guys think? Does sparkfun have something that’s equivalent?

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Thanks for the help guys…maybe I’m over thinking all this stuff which is making it a lot more complicated than it needs to be…

5

jdlev:
Sorry…I’m still learning, and electrical things have been a bit of a black art to me. Looks like this is going to require a lot more components than I thought.

I’ve heard a few analogies of elctricity to water. So voltage would be the diameter of the water pipe, amps would be the rate that the water would flow at…

Correct.

So let’s start at the power supply. AC. The AC naturally has to be broken down to DC which will require a transformer. Couple questions:

First, if you are a beginner with home AC voltage. Please stop now. This is very dangerous. You could lose everything in a fire.

  1. Would it be better to have one large transformer that takes the AC and converts it to straight DC, or should I go with 3 smaller transformers that only draw the required voltage according to each device?

  2. The smaller transformers (like something you’d use to power a cell phone) will take up more space, but I’m guessing I wouldn’t have to use any type of diodes, capacitors, or rectifiers with them would I?

  3. Could I get by with just 2 transformers? One that provides enough amperage to both the 12v devices, and one that has a 6v rating? Or better yet, could I just get 1 12v tranformer, and then have one that provides enough amperage to power all 3 devices with some sort of voltage step down between the device that requires 6-8v…like a voltmeter?

I said I was guessing at the Ah (Amp hours) you are going to use. This will determine how you will design the circuit. It really sounds like you are fixing to get into trouble. Please do some research on different aspects of your project. If you want more help, please post the the specs (product page or datasheet) of each device you are using and a detailed description of your end result. This will let me determine if I want to help you due to safety and liability reasons…

6

I understand…and really appreciate the help. I’m trying to build a simple control panel for my Kamado BBQ stand that I’ve been building. Which means if you help, you get free BBQ :smiley: We compete in the KCBS competition series, and I’ve had issues with temperature regulation. I plan on using a damper and fan to help with that.Here’s the things I’m looking to connect:

A) DC Fan Specs

Dimension

80x80x25mm

Connector

4-pin

Rated Voltage

12V

Rated Current

0.2A

Speed

2500RPM ±10%

Airflow

43.5CFM ±10%

Bearing Type

Sleeve

Noise Level

27dBA±10%

Cable Length

20cm

Weight

53g/pcs

B) LED Light 5 Meter Light Strip

Specifications:

  1. LED Type: 3528 SMD

  2. Color: Blue

  3. LED quantity: 300 LED / 5 Meter

  4. Protection class IP60 (Non Waterproof)

  5. Operating voltage: DC 12V

6.Output power:24W

  1. Viewing Angle: 120 °

  2. Operating temperature: -20 to 50 °

  3. Size: L500cm (5M) × W0.8cm x T0.25cm

10.Source life: > 50,000 hours

Since it says 24watt output…and it’s 12v, I assume it’s 2 amps? I looked all over and couldn’t find any specific reference to the amp draw

C) 20x4 LCD Blue Backlite Display

Interface: I2C

I2C Address: 0x27

Pin Definition : GND、VCC、SDA、SCL

Back lit (Blue with White char color)

Supply voltage: 5V

Size : 60mm×99mm

Contrast Adjust : Onboard Potentiometer

Backlight Adjust : Jumper

I couldn’t find the amps on this one either, but assume the amperage is probably adjustable due to the potentiometer?

D) Motor - I was planning on using this to open the damper, unless you would recommend using a servo instead. The damper is a very thin piece of sheet metal that will be 3-6" in diameter. If the servo is the better choice (as I think it may be if it can handle opening and closing the damper), I included the specs below the motor:

Motor Specs:

Operating voltage: 3V~12VDC (recommended operating voltage of about 6 to 8V)

Maximum torque: 800gf cm min (3V)

No-load speed: 1:48 (3V time)

The load current: 70mA (250mA MAX) (3V)

This motor with EMC, anti-interference ability. The microcontroller without interference.

Size: 7x2.2x1.8cm(approx)

Servo Specs:

Powered by RioRand Advanced Technology

coreless motor,Dead Band Width : 2 usec

Stall Torque : 1.5kg/cm at 4.8V

Voltage : 3.0 - 7.2Volts

Dimension : 22mm x 12mm x 29mm

E) Temperature Sensors x 2 - Max6675 Modules + K Type Thermocouple

Simple SPI serial interface temperature output.

0℃. ~ 1024 ℃. temperature range, the converter resolution of 0.25℃. temperature.

the internal cold junction compensation.

high-impedance differential inputs.

thermocouple breakage detection.

wide operating voltage range 3. 0~5.5V, current 50mA.

working temperature range-20 ℃. ~ 85 ℃.

2000V ESD signals.

Module interface: GND VCC SCK CS SO

Supply voltage: 3~5V DC

Module dimensions: 15mm*25mm

F) Board - I was planning on using either the Due or Mega2560

So that’s it for right now.

7

Boiled down…

A) DC Fan Specs - Rated Voltage 12V, Rated Current 0.2A

MOSFET to turn the motor on/off

B) LED Light 5 Meter Light Strip - Operating voltage: DC 12V, Output power:24W

MOSFET to turn the LEDs on/off

C) 20x4 LCD Blue Backlite Display - Interface: I2C, I2C Address: 0x27, Pin Definition : GND、VCC、SDA、SCL, Supply voltage: 5V

2 wire interface

D) Motor or servo

One wire interface, simple servo output, probably 1.5ms center based, no need for motor driver

E) Temperature Sensors x 2 - Max6675 Modules + K Type Thermocouple, SPI serial interface temperature output, Module interface: GND VCC SCK CS SO, Supply voltage: 3~5V DC

Simple 3 wire interface for each (6 wires total), or 4 wires (CS1, CS2, shared SCK and SO)

F) Board - I was planning on using either the Due or Mega2560.

Overkill by far.

I count 9 lines. Even the most basic, low end, low pin count, cheap Arduino board can handle this. Mega250? Are you kidding? And have 40+ left over lines?

12v battery (direct to fan, LED, and servo), 5v regulator (feeds the Arduino, servo, temp sensors), 2x N channel logic level MOSFETs (fan and LED control lines), 2x 10K pull ups for the I2C on the LCD.

What’s the issue again?

If all this is above your head, you’d better start simple, like blinking an LED and work your way up.

8

I wanted to use the mega or due for future upgrades. I understand all that, and think I can handle it. I just have never dealt with the MOSFETs before…so that’ll be new.

9

Yes you are thinking right. Arduino can’t provide the 12V. So you must go for the Relay operations. You can also use the H-bridge which can also give the facility to you to change the direction of motor. You can easily control the relay driver IC or H-bridge using Arduino.