Alternatively, if you want to increase the power dissipation because of the voltage drop, you can cascode it with a bipolar transistor.

 

https://www.amazon.co.uk/CENPEK-Infrared-Degree-Illuminator-Security/dp/B09H748ZFC/ref=sr_1_5?crid=1BWLZFIG9JW2O&dib=eyJ2IjoiMSJ9.X91XhlWCIPRiobblxWIFkULW9H8snneIhdWq_Cz7jqTxSIBP-NI6-LiFfjHuCqmH0mk-D2zhs041bCo9swGB1tsa1dGRpUw9okuyMq58qWQfZ1kOJrPqVkFSerzSxOBuoWkGWxjStnbcN_renTO0qkmscZIhwv4nJPedO_FUfyXslOPqsU-E_GAFOn6wK7POJS91-9jj6f08M9Qjmc63Yc3QooMd8tqHwXnIsb2okmYt4adJXPKm4ArErm-j5ITxonYEj_n8bVaKFw9CTRXkpQvhtmJspe4hBJwETn3dtMw.lWMy2Qr-6k8ABtTtjfDETBHZLAP_1kwHXpNNfGrFJ7Y&dib_tag=se&keywords=LED+IR+lamp+spares&qid=1720951208&s=luxury-beauty&sprefix=led+ir+lamp+spares,luxury-beauty,64&sr=1-5

well according to the product specs, it consumes 300mA and 48 LEDs. Since they're strung together in both series n parallel, there's no way to know how many mA each one is getting. But if it takes 300mA to illuminate an outdoor field of view, how much does it take for a garage? It's hard to say.

 

Explanation for a basic op amp current controller

 

I n addition to the IRLEDs and the camera you need an actual LOUD alarm for when they actually grab something, so that they decide to hurry away instead. Otherwise you may just have a video of them stealing stuff.

 

A small PNP transistor is recommended to increase the output. The PNP 2N2905 is a compliment of NPN 2N3904
In the study of active current regulating, a common characteristic of certain topologies is ability to current mirror.
It has been speculated that the LM334 inside uses parallel transistors the diagram is just an abbreviation. Not sure?
Related to types of current regulators, it is possible to convert voltage to current or convert current to voltage.
Another type goes further. An op amp, mosfet and sense resistor form a loop capable of actively increasing or decreasing current.
View attachment 326934

yeah the current mirror is a simple enough way to raise the output, but then feedback will occur when the collector current raises Vrset, so it's hard to say where it will reach equilibrium. So i'd have to measure the resulting current. Tryin to figure out if it would be easier than just getting 2 of them in parallel...

 

I n addition to the IRLEDs and the camera you need an actual LOUD alarm for when they actually grab something, so that they decide to hurry away instead. Otherwise you may just have a video of them stealing stuff.

yeah that's true but this (supposedly) is a person that actually lives in my house. A video of the crime is all i need in this case.

 

well that's quite a handy circuit i bookmarked it. For now, though, i ended up using https://www.amazon.com/gp/product/B0D8Z95TWV/ref=ewc_pr_img_1?smid=A1CV2ETGSPQEB3&th=1
these things cost only about $1.30 so they will do for now.

 

Alternatively, if you want to increase the power dissipation because of the voltage drop, you can cascode it with a bipolar transistor.

well that'll work too. my problem is i don't have any parts on hand to try it. all i got is some basic soldering tools, so i just found one on amazon tha looks like it will work https://www.amazon.com/gp/product/B0D8Z95TWV/ref=ewc_pr_img_1?smid=A1CV2ETGSPQEB3&th=1

 

Interesting two-terminal device. Wonder what it contains inside. The CC diodes I am familiar with are JFETs operated at IDSS.

 

Interesting two-terminal device. Wonder what it contains inside. The CC diodes I am familiar with are JFETs operated at IDSS.

yeah me too, don't think it's a CRD.

 

OnSemi produces some devices which are identical or extremely similar. NSI45020AT.
The data sheet description mentions: “The device is based on self-biased transistor (SBD) technology…..” whatever that means.

 

The data sheet description mentions: “The device is based on self-biased transistor (SBD) technology…..” whatever that means.

i don't know either but it might be the same device that i'm using for my LEDs.

 

Reducing error caused by the thermal drift favors the design that transfers heat to the transistor, in turn heat is transferred to
an aluminum heat sink. The accuracy is improved by methods used to keep the temperature as even as possible.
I see fairly accurate controls can transmit and receive control signals using 4 - 20 mA current.
I mention this because history shows they preferred that the current be above 4mA. If paralleling is going to be used the current reference
accuracy could then be better mirrored and compensated from a compliant current reference level. Having a low TC temperature coefficient.
If you know which components are dissipating significant mW of power then constructing the reference current keeping that in mind
where the slope is minimal. The parallel elements can be more complex. It is interesting to see how some of the flat dpak packages are located.

 

I always thought that the purpose of the 4-20mA system was to allow 4mA to run the circuitry that powers the transducer.

 

The reason for the 4mA bottom value current, among other reasons, is also to detect a break in the loop. That is especially important in control systems.
Loop-break detection is vital because: " It is hard to tell the difference between zero and nothing." That is very important in feedback systems.

 

: " It is hard to tell the difference between zero and nothing."

That’s a good way of putting it.

 

self-biased it means it has biasing done internally. no external parts are needed to "program" it for some current. current is fixed. so just pick part number for current you need. (10mA, 25mA...)

 

as for constant current... LM334 is fine for small currents. temperature compensation is used only for precision. not needed here. turning it into something for higher current needs more parts.... and i don't see where all the talk about fancy circuits came from when one could just use a resistor... or LM317 and one resistor. for 300mA the resistor should be 4 Ohm (3.9Ohm will do or two 8.2 Ohm in parallel).

 

One point not mentioned yet is that any linear current regulator will dissipate as much energy as heat as a resistor doing the same current limiting. The best simple scheme for LED current control would be a positive temperature coefficient resistor that would increase resistance as it heated, to compensate for the LED reduced forward voltage as it heated. But making those changes track will be quite a challenge. So just use a series resistor to set the current at 80% of the rating.

 

don't know how to do that. The LEDs are outdoors where there's a big temperature swing.

The datasheet will show you how. You should get one and read it sometime.