What size or how many Relays, building a lamp tower

Thread Starter

Silence820

Joined Nov 14, 2020
3
First, I would like to say I am new to electronics. But since I am stuck in the house, I thought I would give an idea I have for years a try.

I would like to build a lamp tower for my workshop and home. The way it would work, when I enter it will automatically turn off and when I leave, after a short delay it will turn on.

The parts I have up to this point are;

8 55w fluorescent lights

4 ballasts 2x54 watts Philips l-254-uni-r5n2

1 Arduino UNO
https://www.amazon.com/gp/product/B008GRTSV6/ref=ppx_yo_dt_b_asin_title_o00_s01?ie=UTF8&psc=1

1 PIR motion sensor
https://www.amazon.com/gp/product/B0140WFNYQ/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1

1 Timer
https://www.amazon.com/gp/product/B0140WFNYQ/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1

1 cooling fan
https://www.amazon.com/gp/product/B00KF7T9MI/ref=ox_sc_act_title_1?smid=A1Z5H6ZGWCMTNX&psc=1


My primary question is, what size, type, and how many relays do I need?

And would I need anything else for this project?

Any suggestion and/or advice will be greatly appreciated

Thanks.
 

SamR

Joined Mar 19, 2019
3,483
The Arduino can handle small signal relays fine in the 5V coils models. But those relays are typically only rated 1A @ 125VAC or 2A @ 30VDC (you can get larger/higher rated signal relays) so that's good for the fan directly controlled. Or you can use a switching transistor or SCR to drive another higher voltage circuit. Don't know what your voltage is where you live but the big issue is using the Arduino to control higher voltages. Which is not a problem with the proper hardware combinations. So I only see 2 higher rated circuits, the fan, and lights. Adds up to 2 relays/transistors controlled by the Arduino. The fan can be done directly and the second relay to control the lighting circuit. I would also suggest some optocoupler isolation between the Arduino and the higher voltage circuits. Try sketching out the circuit as your information is a bit sparse and needs to be fleshed out a bit. Power MOSFETs would draw less current from the Arduino than a signal relay and can supply fairly high currents.
 

ScottWang

Joined Aug 23, 2012
7,063
The way it would work, when I enter it will automatically turn off and when I leave, after a short delay it will turn on.
Do you mean like this:
when I enter it will automatically turn On and when I leave, after a short delay it will turn Off.

The timer and the PIR motion sensor are the same links.
 

Thread Starter

Silence820

Joined Nov 14, 2020
3
Do you mean like this:
when I enter it will automatically turn On and when I leave, after a short delay it will turn Off.


The timer and the PIR motion sensor are the same links.
thanks for your reply
I would want it to look like someone is there when no one is there
On when I leave and off when I come in.
 

ScottWang

Joined Aug 23, 2012
7,063
thanks for your reply
I would want it to look like someone is there when no one is there
On when I leave and off when I come in.
So the function that you want is to simulates when you are not there, but the lights is on to shows that it seems you are there, it looks like as cheating light?

How is the V/I specification of 55w fluorescent lights ?

I'm thinking what is the convenience way for you to using the MOSFETs or relays to control the lights.
 

Thread Starter

Silence820

Joined Nov 14, 2020
3
So the function that you want is to simulates when you are not there, but the lights is on to shows that it seems you are there, it looks like as cheating light?

How is the V/I specification of 55w fluorescent lights ?

I'm thinking what is the convenience way for you to using the MOSFETs or relays to control the lights.
what do you mean by V/I Specifications?
 

Tonyr1084

Joined Sep 24, 2015
6,243
First, welcome to AAC.

A SPDT (Single Pole Double Throw) relay can be added to a Three Way switching arrangement so that you can turn the lights ON when you want them on. Who would want to work in the dark? When you leave you switch the lights off. Then the PIR (Passive Infra Red) motion sensor can actuate the relay to turn the lights on while you're not there.

But if you want the lights on when you're not there, why turn them off at all? If you only want the lights on at night, then instead of turning the lights on when you leave, just use a photo sensor to detect daylight. Let the sensor turn the lights on at night. Since you want them on when you're not there, I'm assuming you want them on all night. Or even more simply, just turn the lights on and leave them on. No need for fancy switching.
 

MisterBill2

Joined Jan 23, 2018
9,233
The functionality described is close to what you will get using a standard PIR security light controller and an external relay to invert the logic. But if you wanted the lights to come on when you entered then you would not even need the arduino and it's power supply and interface. The 8 lights at 55 watts each will bring the load up to about 5 amps, and so a relay with ten amp rated contacts would be a good choice.
A cheap motion sensor security light assembly will all ready have the UL approval and all of the AC wiring already done, so all that you would need to do is replace the lights connection with the 120 volt relay coil. Much simpler and a lot safer than messing with an arduino to try and control the lights.
 

MisterBill2

Joined Jan 23, 2018
9,233
The application sounds a bit more like a grow room for plants, and switching off the grow lights when one enters to harvest. Also, the TS did not ask for random lighting. And using an available controller would avoid the effort of needing to package the controls to make the system safe to be around.
Using an aduino sounds too much like a nuts-and-volts solution, intended to sell arduino stuff.
 

LesJones

Joined Jan 8, 2017
3,476
I don't see how a PIR detector can tell the difference between you entering the house and leaving it. I think you would need two light or IR beams spaced about 6 inches apart to decide the direction that you are moving.

Les.
 

Tonyr1084

Joined Sep 24, 2015
6,243
the TS did not ask for random lighting.
The TS DID say he wanted it to look like the room (or house or apartment, he/she didn't say) wants the room to look like someone is there. Lights always on only looks like lights on. Lights switching on and off at irregular intervals looks more lived in. That's what I assumed the TS wants to achieve, make a room look like it's occupied.
 
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