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Excessive heat from my l7805cv voltage regulator? Answered

Hi, I'm a newbie and I've set up a programme using an Arduino Nano to build a high speed photography project using Bluetooth  (from a guy called ZHUT on youtube).
 I've used his schematic and  his App and it's almost there, but the l8705cv regulator is heating up fast (almost too hot to touch) after a few minutes( with a heatsink). I'm using a 9 volt dc adaptor, power coming out is 5 volts. The trigger threshold numbers (1023) don't come up on the app. to start the programme running, stays at zero.  I've never used a schematic before, so I think I've wired up something wrong to cause this. 
Any suggestions would be really welcome, as I've spent a long time on this and I'd love to get it going.
I'll send photos, hope they will help, thanks 

Discussions

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apatrik

Best Answer 1 year ago

Hello, first of all make sure you have not made cabling errors, if everything is ok I can give you two simple suggestions to improve your project,

1) remove the double sided adhesive from the heatsink and secure it to the regulator by means of a small spring, or by means of a small bolt, the direct contact between the two metals will make the heat better dissipate.

2) replace the 9v battery with 4 1.5 AA batteries, this lowering of voltage will greatly reduce the dissipation on the controller, moreover you will have a greater autonomy.

I hope it helped youHi, I can give you two simple step to improve your project

1) take away the bihadesive from the heatsik and assicure it to 7805 with a little spring

Ciao,prima di tutto assicurati di non aver commesso errori di cablatura, se tutto è apposto posso darti due semplici suggerimenti per migliorare il tuo progetto,

1) togli il biadesivo dal dissipatore e assicuralo al regolatore tramite una piccola molla, o tramite un piccolo bullone, il contatto diretto tra i due metalli farà didssipare meglio il calore.

2) sostituisci la batteria da 9v con 4 batterie da 1,5 AA, questo abbassamento di tensione ridurrà di molto la dissipazione sul regolatore, inoltre avrai una maggiore autonomia.

Spero ti sia stato d'aiuto

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0rangeapatrik

Answer 1 year ago

Hi Apatrik, bolted my heatsink to the regulator after cleaning the surfaces, plugged in my 9 volt adapter and after 10 minutes it was just warm even with the LED lamp burning----Heat problem solved! going to adapt a battery holder to hold 4 x 1.5 batteries as you've suggested .

Many thanks for your help with that problem, can you tell me if my photos came through, I had a problem sending them ?

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johnip4

1 year ago

if you switch to 4 1.5V batteries the regulator is redundant. The Arduino has its own regulator. The only issue could be th he-06, is rated for 6v but to be on the safe side you can power it from the 5v pin on the Arduino. The rest of the circuit doesn’t require a precise voltage and will be fine at 6v.

YMMV, I’ve released a lot of magic smoke in my time.

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seandogue

1 year ago

It has been my experience that 78xxx seris regulators require considerable heat sinking to operate anywhere near their max threshold.

In addition, the ideal source voltage for a linear regulator of this type should be only a few volts greater than the output voltage to minimize resistive heating in the IC due to its natural dissipation (ie, say you're operating a 5VDC 7805 reg, from a 12VDC source, with a load current of 0.5A...that means you are dumping about

(12-5) x 0.5 = 7 x 0.5 = 3.5W in heat.

So...

Use a lower source voltage per above

Reduce your load current.

If you don't actually "need" a linear regulator, use a switching regulator instead. They're more efficient.

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0range

1 year ago

Sorry, I thought photos had sent, I'll try again.

DSC_0021.JPGDSC_0023.JPGDSC_0026.JPGDSC_0032.JPG
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Josehf Murchison

1 year ago

Links, schematics, something, please.

LM7805 has short circuit protection so my guess is it is loaded to the max.

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steveastrouk

1 year ago

How much current is your project drawing ?

Post your schematic, so we can see what its supposed to do - I'm not wasting my time digging for it.

Its either pulling too much current, or your heatsink is inadequate