External Power Supply – HELP

I copy/pasted this from WORD. I can't seem to get the spacing to work correctly on the top portion of my post. What's the trick?

This is a list of my projects current draws

Qty Item ea Subtotal (Milliamps)
4 1602 21 84
5 2004 75 375
1 arduino 70 70
3 Relays (always on) 75 225
3 Relays (momentary on) 25 75
10 LEDs 25 250
TOTAL: 1079 or 1.1 amps

Assuming the 1602 & 2004 & relays & LEDs can each handle 9 volts can I do this.
First electrically separate the arduino board from the extras. Then purchase a 9V 2A power supply. Then split the 9V output into two separate leads. Send one lead to the AC socket to power the board all by itself. Send the other lead to power all the extras.

Never assume. Check the product data sheets.

LEDs as single components have current limitations, not voltage limitations. Always use the correct current limiting resistor to stay below the manufacturer's recommended maximum operating current.

Most of the items will be toast, destroyd, exposing them to 9 volt.

Like this:

Qty Item                   ea   Subtotal (Milliamps)
4   1602                   21      84
5   2004                   75     375
1   arduino                70      70
3   Relays (always on)     75     225
3   Relays (momentary on)  25      75
10  LEDs                   25     250

Use the </> icon for preformatted text.

Why not use a 5V cell phone charger? Right voltage and probably cheaper since they are so common. I pick them up at the local thrift shop cheap - test then before use of course :slightly_smiling_face:.

1 Like

Please post a wiring diagram. We need to understand how your power is distributed, what voltages the devices use.

@ken52 did try; see the edit history of the opening post. But it did not quite work out :wink:

@ken52, Your topic has been moved to a more suitable location on the forum. Installation and Troubleshooting is not for problems with (nor for advice on) your project :wink: See About the IDE 1.x category.

Let’s go about this from a different direction. Now that my project is complete and tested I need to disconnect the Arduino from the USB. Therefore I will need an external 5V 2A power supply. Because this is my first project I don’t have this answer.

I have found many power supplies out there but the product reviews are horrible. What is every body using? And in the case of needing 2 amps of power should I purchase two 5V 1A supply’s? One for the Arduino and the other for the extras (LCD, relays and the like).

You could as long as they agree on where to jump off from, in other words, connect the grounds.

if this is your first project and you plan on making more, use a homemade benchtop supply: 3.3v, 5v, 12v converted out of an old PC PSU. Tons of tutorials on how to do this. It's really easy, just take your time.

Pray tell, what are 1602 and 2004?

If you are using the typical "Blue Songle" then you will have even earlier failures if powered with 9V.

How simple, love it! The best part is that I also needed 12VDC for the linear actuators. Does the PC P/S only draw as much AC power as needed for the 5 VDC and 12 VDC needed or does it always run flat out at the stated wattage on the P/S unit? Or should I find the lowest powered P/S?

I have another problem that needs solving. This project needs to know when the cooling side of the HVAC thermostat is active. That’s easy enough in that all I need to do is see if there is 24VAC on the wire going back to the HVAC control board. How do I go about doing this? Do I simply use a 24VAC relay to activate a 5VDC signal back to the arduino? I know that you need a diode across the coil side of a DC relay. Do you use 2 diodes on AC?

Not often used with an AC relay coil.

In some situations, a capacitor and resistance snubber is used, MOV, back to back Zeners rated more than the applied AC peak voltage.

Or use an SSR.

An AC capable opto coupler can be use for feedback.

image

I am looking for some knowledge on SSR’s. As unusual as this might seem I am looking for an SSR that will control a lower voltage from a higher voltage. My signal is 24 VAC. (From HVAC transformer). And the other side of the SSR is 5 VDC (Used as input to an Arduino). Basically, when the house thermostat turns on the A/C I want my Arduino to know it. I don’t want the SSR to be a big drain on the HVAC transformer. What Size/Type/Model No should I purchase?

I have never seen an SSR with AC control and DC output. You should google it yourself as no one can see everything that is possible out there.

My suggestion is an Opto Isolator as suggested by @LarryD (on the right of his post).

For my 24 VAC sensing I use a Opto = Fairchild FOD814A300 with a 20 K ohm resistor in series with the opto. Then I add a 1 µF capacitor on the output.

Or you could use a 24Vac mechanical relay.

John

Don't use a word processor. Use a text editor or just type in the forum editor.

No one is going to be able to help you without a schematic. Please, no Fritzing crap- that will reduce the pool of people willing to help. Pencil and paper is fine.

If I understand you correctly, this is the wiring.

Close but no cigar :slight_smile:

The 20k end would go from the 24Volt thermostat to the thermostat common (often identified by "C")

In your drawing the inputs to the 20K + opto are shorted together, no voltage for the opto to sense.

You should probably explain your system better.

What are the wire colors between thermostat and controller? Are there any "spare" wires that are not connected? What color?
Common colors (in US) are:
RED...................... 24VAC (hot)
BROWN 24VAC...... (common)
WHITE.................... heat
YELLOW................. cool
GREEN..................... blower
BLUE or ORANGE....heat pump reversing valve

I am not an electrical engineer or electrician. However I thought the reason for the 20K ohm was to reduce the current draw of the opto. I really don't understand the reason for adding the 20k ohm across the 24VAC and ground wires I left the resistor out of my diagram so that after you explain it to me I can add it to the correct location without needing an eraser !

Still too many questions.