What kind of info would be useful?

It runs through the entire project, starts with how much power your supply can deliver. Power is not volts, it's not amps, it's watts. Watts is calculated by multiplying the voltage times the amperage. That is to say - the wattage the system will draw from the PS (Power Supply). If the supply is capable of 12V at 2A then that's 24 Watts. If the PIR draws 12V @ 300mA (0.3A) then that's 3.6W used by the PIR just to function. Then from there the power has to be sent to the LED's. IF the LED strip draws 3A at 12V then that's 36W. Add the LED strip and the PIR and that's 39.6W. That's 15.6W more than the PS can deliver. The voltage will fall off and the LED's won't light, either because the strips draw too much power or there's not enough power for the PIR's. Without knowing all the specifications nobody can guarantee a functioning system. Keep in mind that you're wanting to run TWO PIR's.

We need to know
How much power can the PS deliver?
How much power does the PIR draw?
How much power can the PIR control?
How much power does the LED strip draw?

 

I was asking if the 12 volt power supply connector is compatible with the power connector on those PIRs you have now.

 

The listing shows it as suitable for led lights, says it has a range of 5 - 24v and is 5A and DC.

Not all LED's are the same. 5 - 24V may be the voltage the PIR can operate on. Minimum is 5V and max is 24V. But remember, it's not just volts. It's not just amps. It's watts

I saw these that claim to be for led strips would they be better?

The link is to microswitches. I thought you decided against that.

 

IF the PIR module does include the terminal strip adapter as shown, then wires from an adequate power supply can be connected to feed power to both PIR devices. AND IF the terminals are correctly marked on those adapters, then probably the polarity will be correct. And if the watts available from the supply are adequate then it should work.

 

Not all LED's are the same. 5 - 24V may be the voltage the PIR can operate on. Minimum is 5V and max is 24V. But remember, it's not just volts. It's not just amps. It's watts

The link is to microswitches. I thought you decided against that.

Weird. I thought it was to other pirs but clearly not. Thank you for the detailed explanation about watts, I learnt something. The LED is 12v but I don't know what wattage... I'll see what (watt ) I can find out. Again, thank you.

https://www.amazon.de/-/en/Motion-S...2a-aaa8-b1298e2b0e23&pd_rd_i=B0CQXS9M3T&psc=1

 

I was asking if the 12 volt power supply connector is compatible with the power connector on those PIRs you have now.

Oh I see, sorry. Yes they're compatible.

 

Post links to the 12 volt power supply and LED strip please.
Need to know if the supply can handle the current the LED strip will draw.

 

LED's are not voltage dependent. They are current dependent. That is to say you set up an operational parameter that considers first what current you want flowing through them. In the case of those 12V strips, they have built in resistors that limit the current to the LED's. IF the LED's are running at 20 milliamps and are powered from a 12 volt source then the built in resistors are likely 600Ω. This sets up a current of 20mA through the LED's. Now, I don't KNOW that those LED's are running at 20mA, it's just a common value for small LED's, though not necessarily 20mA. There are some that run on 700mA. I doubt yours are. The strip LED's I have use a 120Ω resistor. So that's 100mA. 12V @ 100mA = 1.2 Watts. Or 1200mW.

In theory you can have ANY voltage operate the LED's. I said "In Theory". You could have 12 million volts and 120KΩ and they'd operate (in theory) normally. The wattage would be very different, and you'd have to manage an astronomical amount of wattage.

Coming back to reality; if your LED strips are anything like the ones I have at my work station then my supply would need to be capable of a minimum of 100mA @ 1.2W, as I said in the first paragraph. MY wall wart is capable of 2A as is stated on the supply. So I could run much longer strips than just the single 16 foot strip. Similar colored LED strips I have are strung together in a set of four strips and the PS has no problem driving all of them. My PS is capable of 12V @ 24W. That's not big at all. But it's big enough. That's why I made the point about accounting for all the components on the circuit and how much power they're going to need, and whether or not your supply can deliver it.

As I said, LED's are not voltage dependent. They are current dependent. Even though we're talking about wattage it's the current that is the first consideration for the LED's. Voltage is secondary. Supply is next, and finally the wattage is considered. Wattage is how much heat is going to be produced by the circuit. High wattage, like a high wattage lamp, means a lot of heat to dissipate. The lower the wattage the less heat that needs to be managed.

So to give you a final answer on what you need to make it all work - all that information is critical.

 

LED's are not voltage dependent. They are current dependent. That is to say you set up an operational parameter that considers first what current you want flowing through them. In the case of those 12V strips, they have built in resistors that limit the current to the LED's. IF the LED's are running at 20 milliamps and are powered from a 12 volt source then the built in resistors are likely 600Ω. This sets up a current of 20mA through the LED's. Now, I don't KNOW that those LED's are running at 20mA, it's just a common value for small LED's, though not necessarily 20mA. There are some that run on 700mA. I doubt yours are. The strip LED's I have use a 120Ω resistor. So that's 100mA. 12V @ 100mA = 1.2 Watts. Or 1200mW.

In theory you can have ANY voltage operate the LED's. I said "In Theory". You could have 12 million volts and 120KΩ and they'd operate (in theory) normally. The wattage would be very different, and you'd have to manage an astronomical amount of wattage.

Coming back to reality; if your LED strips are anything like the ones I have at my work station then my supply would need to be capable of a minimum of 100mA @ 1.2W, as I said in the first paragraph. MY wall wart is capable of 2A as is stated on the supply. So I could run much longer strips than just the single 16 foot strip. Similar colored LED strips I have are strung together in a set of four strips and the PS has no problem driving all of them. My PS is capable of 12V @ 24W. That's not big at all. But it's big enough. That's why I made the point about accounting for all the components on the circuit and how much power they're going to need, and whether or not your supply can deliver it.

As I said, LED's are not voltage dependent. They are current dependent. Even though we're talking about wattage it's the current that is the first consideration for the LED's. Voltage is secondary. Supply is next, and finally the wattage is considered. Wattage is how much heat is going to be produced by the circuit. High wattage, like a high wattage lamp, means a lot of heat to dissipate. The lower the wattage the less heat that needs to be managed.

So to give you a final answer on what you need to make it all work - all that information is critical.

Thank you for the 101 electrics course here! So my question is (and sorry but seeing as you're teaching me stuff), what is the difference then between Watts and current please?

 

Post links to the 12 volt power supply and LED strip please.
Need to know if the supply can handle the current the LED strip will draw.

Hi,

It's nothing exciting, just this cheap as chips adaptor, I was going for 12v as the LEDs are. If I need to get something else please let me know
https://vi.aliexpress.com/item/1005...t_main.17.34061c24k7Yuio&gatewayAdapt=glo2vnm

 

Says power supply rated 2 amps.
What about a link to the LED strip?

 

Says power supply rated 2 amps.
What about a link to the LED strip?

Apologies if I've not been forthcoming here are links to all items for the project, hope that's helpful

Adaptor
LED strip (12V)
PIRs

 

The specs on the LED strip indicate 10 watts / meter length.
That 12 volt adapter can only drive a 2 meter length of LED strip.
How long a strip is needed?

 

The PIR motion relays would have their current limitations stated in amps, while the LED strip is probably specified in watts, but probably with a voltage requirement given.

 

The specs on the LED strip indicate 10 watts / meter length.
That 12 volt adapter can only drive a 2 meter length of LED strip.
How long a strip is needed?

The stip is 5 metres, I don't intend to cut it but the cupboards are about 3 metres in total.

 

Going to need a bigger power supply!

 

Current is a measure of the flow of electricity. Examples of current are AC and DC. AC is "Alternating Current". That means it goes one way, then changes direction and goes the other way, then changes again. And again and again. In the USA it changes direction 120 times per second. A single period of an AC wave is one cycle. Starting at zero, it climbs to max POSITIVE volts, changes direction, crossing zero volts then reaches its max NEGATIVE voltage, then heads back to where it started from - zero volts. It keeps doing that as long as they're generating power at the power plant. That 60Hz is AC Hertz. Other examples of AC is radio transmission which can be in the megahertz, audio signal such as the music coming out of your speakers. The signal keeps changing with the music. High frequency notes have high frequency AC. Low frequency - you guessed it. Without AC you wouldn't have music.

OK, car radio's work on DC or Direct Current. Yes, that's true. DC current is current that always moves in one direction. From Positive to Negative. A battery powered device is DC. So are the LED's in your thread. The LED's work on DC. The power supply (PS) transforms 120VAC (Volts Alternating Current) into 12VDC (Volts Direct Current). DC can be pulsating or can be constant. It can pulse from zero volts to (in this case) 12 volts then back down to zero volts. But it never goes negative. Only AC does that.

what is the difference then between Watts and current please?

Watts is a measure of power. How much effort is being exerted. Horse power is also measured in Watts. 550 Watts is equal to 1 horse power. It's the work that is being performed. The value of watts is calculated by multiplying the voltage times the current. This is done in DC terms while in AC terms it's expressed as VA or Volt/Amps. Since AC is always changing so is the - um - wrong term here - wattage. VA is an expression of time and I'm not well versed to explain that.

In your project you have a power brick (assumably) that runs on (probably) 100 to 240VAC and transforms that to 12VDC. IF your circuit is running at 100mA and 12V then 100mA x 12V = 1.2 watts. That paints the whole picture. It's volts times amps to equal watts. Know any two of those and you know the voltage. 1.2 watts divided by 12 = 0.1 A (100mA) and 1.2 watts divided by 0.1A = 12V.

I'd recommend clicking on the education tab and explore some of the topics. One I'd point you to right now is "Ohm's Law".

'av'a g'day.

 

Going to need a bigger power supply!

to go with my boat? hahaha! Thank you. What am I looking at?

PS I actually have another LED project I need to do in my kids' room. I had actually wondered if I had enough power but wasn't sure how to work it out. Would you be okay with me messaging you about it? No PIRs this time

 

Current is a measure of the flow of electricity. Examples of current are AC and DC. AC is "Alternating Current". That means it goes one way, then changes direction and goes the other way, then changes again. And again and again. In the USA it changes direction 120 times per second. A single period of an AC wave is one cycle. Starting at zero, it climbs to max POSITIVE volts, changes direction, crossing zero volts then reaches its max NEGATIVE voltage, then heads back to where it started from - zero volts. It keeps doing that as long as they're generating power at the power plant. That 60Hz is AC Hertz. Other examples of AC is radio transmission which can be in the megahertz, audio signal such as the music coming out of your speakers. The signal keeps changing with the music. High frequency notes have high frequency AC. Low frequency - you guessed it. Without AC you wouldn't have music.

OK, car radio's work on DC or Direct Current. Yes, that's true. DC current is current that always moves in one direction. From Positive to Negative. A battery powered device is DC. So are the LED's in your thread. The LED's work on DC. The power supply (PS) transforms 120VAC (Volts Alternating Current) into 12VDC (Volts Direct Current). DC can be pulsating or can be constant. It can pulse from zero volts to (in this case) 12 volts then back down to zero volts. But it never goes negative. Only AC does that.

Watts is a measure of power. How much effort is being exerted. Horse power is also measured in Watts. 550 Watts is equal to 1 horse power. It's the work that is being performed. The value of watts is calculated by multiplying the voltage times the current. This is done in DC terms while in AC terms it's expressed as VA or Volt/Amps. Since AC is always changing so is the - um - wrong term here - wattage. VA is an expression of time and I'm not well versed to explain that.

In your project you have a power brick (assumably) that runs on (probably) 100 to 240VAC and transforms that to 12VDC. IF your circuit is running at 100mA and 12V then 100mA x 12V = 1.2 watts. That paints the whole picture. It's volts times amps to equal watts. Know any two of those and you know the voltage. 1.2 watts divided by 12 = 0.1 A (100mA) and 1.2 watts divided by 0.1A = 12V.

I'd recommend clicking on the education tab and explore some of the topics. One I'd point you to right now is "Ohm's Law".

'av'a g'day.

To be honest Tony, as much as I will certain look into learning more partly because my son likes to tinker and it'll help with supporting him as he builds stuff, I think I've learnt more reading your responses than anything I've ever read on the subject. It really has been like reading with all the lights on. Thank you so much, you've definitely taken the befuddlement out of this and that's enough to make me want to read a bit more. Probably get myself a simplfied book for Christmas, then my son can read it afterwards. Appreciate your help and input.

 

to go with my boat? hahaha! Thank you. What am I looking at?

PS I actually have another LED project I need to do in my kids' room. I had actually wondered if I had enough power but wasn't sure how to work it out. Would you be okay with me messaging you about it? No PIRs this time

Sure