Hello.

I want to make a simulated security camera. The idea is that the IR leds emits at night in case the thiefs check that. I´m going to put 27 IR leds.

If my calculations are right, the IR led works with 1,2V and 20mA. I´m going to power it with a rechargeable lithium battery 3.400 mAh and 3,7V. I´m going to put 9 groups in parallel of 3 led in series, so the voltage drop in each series will be 1,2x3 = 3,6V and the total current will be 20x9 = 180mA. But this only gives me 3400/180 = 18,9 hours. Is that right?

If this is the case I´ll need to power it with a power supply. And the other question is, do IR leds dissipate a lot of heat?

Thank you.

Best regards

 

hi Ruf,
IR LED's in the dark glow a very low Red light, not visible until you are very close to the LED's
How will that deter a thief.??
E

Update:
Consider using one RED LED, set to blink on for a short flash, say every second..
Your batteries would last much longer and the thief would see the flashing and think its an active camera

 

A Lithium 3.7V battery is 4.2V fully charged.
A "1.2V" IR LED has a range of forward voltage from 1.1V to 1.3V.
Then three 1.1V LEDs powered from 4.2V will draw maybe 20000mA and blow up.
LEDs always need a series current-limiting resistor and a little extra voltage for it.

The"3.7V" battery will be 3.0V when it is discharging and three 1.2V or 1.3V LEDs will produce no current or IR.

 

Thanks for your answers. Yes, I know IR is invisible, but it is easy to see with the camera of the cellphone. It appears as a purple light.

Ok, I didn´t know that about leds. Thanks for the advice. So, in any case, I´ll need a power supply if I want the leds last running for more than 1 or 2 days right?

 

You can use a battery if it is huge and you charge it often enough. Since a single lithium battery cell voltage is too low for three 1.3V IR LEDs and the diode and current-limiting resistor need extra voltage than the 3.0V battery can produce, use two LEDs in series with a current-limiting resistor. Maybe the LEDs will not be too dim when the battery voltage has dropped to 3V.

 

I´m going to put 27 IR leds.

27 LEDs are good if you want to see in the dark.

but it is easy to see with the camera of the cellphone.

I think one IR LED can be seen by the cellphone. But you should build a 1 LED light and see before you build 27 LEDs in a circuit.

 

thanks for your answers

 

LEDs do generate heat, and heat is the enemy of LED life. The heat generated is about the same a the DC power input, So you can use that for determining the size of the heat sink. And if you can use a motion detector to trigger the LEDs your battery will last much longer.

 

LEDs do generate heat, and heat is the enemy of LED life. The heat generated is about the same a the DC power input, So you can use that for determining the size of the heat sink. And if you can use a motion detector to trigger the LEDs your battery will last much longer.

Hey! Nice idea about the motion sensor.

 

hi Ruf,
The low cost PIR sensors do not have any current drive capability for driving LED's
You would need additional devices to power LED's.

E
Look here:
https://www.ebay.co.uk/sch/i.html?_...=0&LH_TitleDesc=0&_odkw=PIR+sensors&_osacat=0

 

As a one off, you will probably spend more for your mock camera than s real one.

Bob

 

Thanks for yor answers. The problem with a real camera is I´ll need a power supply and I want to run it with battery

 

hi Ruf,
My security PIRs [ same as the eBay link] use about 50uA when not activated.
Use a MOSFET on the to 3V out signal when activated, to enable a Boost SMPS to get 12V for the camera, which is only ON when activated.

Why do want to use only a battery supply.??

E

They work OK in Pompey, so they should be OK in Soton.

Update:
Look here.
https://www.ebay.co.uk/sch/i.html?_....m570.l1313&_nkw=DC+to+DC+boost+smps&_sacat=0

This one should OK depending upon the Camera you choose.
https://www.ebay.co.uk/itm/384103151784?hash=item596e54f8a8:g:ZhIAAOSwzeBgfHtc

 

hi Ruf,
IR LED's in the dark glow a very low Red light, not visible until you are very close to the LED's
How will that deter a thief.??
E

Update:
Consider using one RED LED, set to blink on for a short flash, say every second..
Your batteries would last much longer and the thief would see the flashing and think its an active camera

I dont know, but do any real security cameras have flashing red leds ?

 

If the array of 27 IR LEDs blinks once per second then it will appear that it is taking one picture per second, That is a believable rate for a security camera. And the short blink will use far less power. And it will be more obvious to a cell phone.

 

Given you are only trying to simulate a security camera, why not consider using ordinary red LEDs and running them at a very low level, so that they match the apparent dim light from IR LEDs? They'll be a lot cheaper than IR, they'll use a tiny fraction of the current and you'll only see the difference on a mobile phone - and not much there either, as low-level red LEDs show up quite brightly and could easily be confused with IR. Use something simple like a 555 to give a M/S ratio of about 50:1. Your batteries will last for weeks!

 

The thiefs in my neighborhood are very smart. If they realise the camera is fake it could be even worse.

The solution given by ericgibbs looks very good option. I´ll try that, but thank you for all the people taht had helped me.

 

Why are you bothered by thieves? Do you leave money and valuables laying around outside the locked door of your home at night? No street lights? Do you live in a wild jungle instead of in a civilized city?

Do not assume that every area i free of bad actors. There are always those who choose to rip off others, and it really makes no difference how many precautions one takes or how well one keeps everything of value out of sight.
The fact is that only in that mythical Kingdom of Utopia will you find absolute perfection and not a single bad actor.
Consider now that in a city of 100,000 people, if 99.9% of them are totally honet, that still leaves 100 that are not honest.

 

Why can't the 100 thieves in your little town act like normal humans instead of like animals?
Was it their parents or their school that taught them how to become animals?
Maybe nobody told them the consequences of being a criminal (prison).

I have no idea why some people are rotten criminals. In addition, I lack the authority to force people to act properly. And now I am really wondering what part of the world you live in, since I have never been aware of any place where every person always behaved perfectly all of the time. I never knew that UTOPIA actually existed. OR, possibly it is a police state.

 

The thiefs in my neighborhood are very smart. If they realise the camera is fake it could be even worse.

The solution given by ericgibbs looks very good option. I´ll try that, but thank you for all the people taht had helped me.

if you have a smart thief problem, I don't think that anything short of a Rottweiler on the loose will have any effect.
The smart thief almost certainly not show their face, Covid masks make hiding your face no longer suspicious and they will ditch their clothing on the way home.
I wouldn't be messing about with fake systems as they tend to be identifiable. A CCTV warning sign might be just as effective.
Published camera footage shows that even real cameras are no deterrent to determined thieves and footage is poor quality.
My next door neighbour has been broken into four times and every ground floor door has been trashed, and that was despite a professionally installed alarm system. I suspect that the system might have worked, but probably never maintained.
On the last occasion, finding nothing left to thieve, they went on to do his other neighbour's property.
What has helped the thieving low life has been the local council decision to turn the street lighting off after midnight.
I would be beefing up things like door and window security and using insurance approved door locks etc.
Realistically, nothing less than a steel door and steel frame is going to stop a break-in. Police can gain entry in drugs raids way before the occupants wake up.
The other thing they don't like is being lit up with some decent powerful lighting which is what I had to do.
I can't prove that it works as a deterrent, but so far so good.