I need to lower 24V to 12V at 1A for 60 devices, automotive, due Wednesday

[Niklas]

You can offload some of the dissipation in the 7812 by adding diodes in series with the input. 1N540x can dissipate the power loss without a heatsink. Indicated thermal resistance is approx 20'C/W with short leads compared to >50'C/W for the smaller 1N400x. Something to think about to secure operation on a hot summer day without good ventilation.
Another option is to add a 7818 regulator as a preregulator to split the dissipation.

[Zero999]

If his "ready-made device that takes a 12V 1A" is designed to run in a car it will surely account for all that already.

It was designed to run off a wall adapter.

I have taken apart the device. The power circuit is behind a shielding can.  I think I can pop the lid off that can. Let me check...

It appears I'm on your ignore list!

What did I do? If you don't respond to this soon, I'll have to put you on my ignore list, so I no longer waste my time on you.

[ivan747]

If his "ready-made device that takes a 12V 1A" is designed to run in a car it will surely account for all that already.

It was designed to run off a wall adapter.

I have taken apart the device. The power circuit is behind a shielding can.  I think I can pop the lid off that can. Let me check...

It appears I'm on your ignore list!

What did I do? If you don't respond to this soon, I'll have to put you on my ignore list, so I no longer waste my time on you.

Hey! Sorry for not replying! The converters look really nice and they're cheap.
Unfortunately they said it's too risky to ship stuff, any delay and we're screwed.

If the solution we end up going for is a temporary one (something like the 7812s), I think this converter is high on the list:
https://www.mouser.com/ProductDetail/CUI/VXO78012-1000?qs=sGAEpiMZZMsc0tfZmXiUnQ%252bwKZhbvwnuBKzimGXrb31aIcHwaSyVLA==

It would make a good 7812 drop-in replacement.

[ivan747]

Sitrep:

Turns out half the vehicles had 24V to 12V step down converters for the stereo, so we took power from there. They were in a convenient location as well.

The other half didn't have anything. I called around and found a shop that had the exact amount of step down converters I needed. Again, these were specifically designed for connecting 12V car stereos to 24V vehicles. I still wish I had some kind of extra filter, but that's the only thing I got.

I took one apart and it just looks like there is one IC doing the job, the construction of the device is not that great... I didn't examine it very closely, as I didn't have much time. Hopefully its design filters out some of the brutality that you find in an automotive electrical system. As for thermals, I think it will be alright, we are using less than 20% of the current that it promises to deliver.

If you are curious, it looks something like this:

https://www.amazon.com/Pyle-PSWNV120-Power-Converter-Technology/dp/B003P1D82S/ref=sr_1_36?ie=UTF8&qid=1518487542&sr=8-36&keywords=24v+to+12v+step+down+converter

Thank you all for your help! It was nice to know I had from plan A to plan Z.

[sokoloff]

Really appreciate when people come back and tell us how things went. Thanks for that!

[rsjsouza]

Good that everything was solved nicely, Ivan! I was almost at the point of telling you to slap a 12V/6~12W in series with the load. 

I was following this thread with interest as I have seen myself in these hot waters quite a few times in the past when I lived in Brazil; sometimes the opportunity is too good to pass ($$$ or prestige), the schedule is insane and the local market is anything but crappy or "creative" (shoehorned) solutions. At least there, counting on a scheduled delivery on something coming from a foreign country is the same as playing roulette - one disgruntled or greedy customs agent and your package takes months to be freed.

[ivan747]

Just came back from finishing the installation. What a job! It took three of us two full days and a handful of extra DC-DC converters, as some pre-installations were not working. The extra ones were totally overkill, they were huge (15A). But that's what was available.

Lessons learned:
*Support from your people is the best support you have.
*You can stick anything with 10lbs double sided tape as long as it's clean.
*3M tape is the best tape.
*You can't describe a connector over the telephone.


Everybody seems happy!
Thanks guys!