How to use a voltage regulator L7805 as a constant current LED driver

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A complete guide for GCSE Electronics students who might want to use a high power LED (e.g. 1W) in their circuits and build a constant current driver using a linear voltage regulator such as the L7805 / LM7805

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@pilotox 2 жыл бұрын

Hi! Thanks for the video! I was looking for a temporary solution to drive a LED and your solution is quite nice!

@PizzeyTechnology 2 жыл бұрын

Glad I could help

@ShopperPlug 11 ай бұрын

Can you make a video on this but for LM317 for constant current source? Will be used for laser TTL.

@mikpiotto 10 ай бұрын

would LDO voltage regulators work in this instance too?

@sesvid 3 жыл бұрын

Hi! Thank you very much for your video. Very helpful! At about 9:05 you said that the output of the regulator needs a load. But what if the LED burns over time due to aging and it would wouldn't be replaced for a certain period of time, can the L7805 get damaged? Thank you in advance.

@PizzeyTechnology 3 жыл бұрын

A component can fail open or closed (short). If it fails open then no current will be drawn. A constant current driver will then increase the output voltage in an attempt to drive the current. On the other hand, if the LED fails shorted, the constant current driver will reduce the output voltage to limit and therefore maintain the constant current.

@sesvid 3 жыл бұрын

@@PizzeyTechnology Thank you very much for the answer. So if the component fails open, the regulator will slightly increase the voltage but since no current is flowing, there is no danger for the regulator to get destroyed, even not after a long period of time. But if the component fails short, the current flow from the regulator will be very high. But since the regulator has a built-in short circuit protection, I suppose that the regulator will not overheat or even get damaged, even if after a long period of time. In that case, the regulator could even act as a short circuit protection to the circuitry as well as for the power supply prior to the regulator. Are my thoughts correct? Thank you very much ones again for your help 👍 Btw, subscribed to your channel.

@PizzeyTechnology 3 жыл бұрын

@@sesvid Nearly there, but not quite right. If the load fails "open" the constant current driver will not "slightly increase the voltage" -- it will increase the voltage as much as it can. This will be limited by the supply voltage (Vs or Vin) and the regulator drop (Vd). However, with no load current there will be no significant current through the voltage regulator. Power dissipated (P = VI) will therefore be minimal. No power = no heating. Thanks for the subscription.