7805 running hot but clock is running fine

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2 years 1 month ago #9097 by Ian
A linear regulator is always going to dissipate some heat, that is their nature. However, I'm glad that it is working for you. If you do get the buck converters, please let me know your experience with them!

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2 years 1 month ago - 2 years 1 month ago #9098 by Torsten Lang
Hi Pjotrke,
hi Ian,
there are several drop-in replacements for the 7805/7905 series LDOs. I would always go for a product of a renowned brand instead of some cheap no-name China product. Ty already pointed you to the muRata modules, I personally don't know these, but I already used the RECOM R-78 series or the TRACO POWER TSR 1 series. I already used both of them and have no complaints, the muRata are cheaper than the RECOM or TRACO POWER modules, I just have no personal experience with them.

With best regards,
Torsten
Last edit: 2 years 1 month ago by Torsten Lang.

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2 years 1 month ago #9099 by Ty_Eeberfest
The Murata buck converters I have used are actually the older (and more expensive: $10.00) ones:
www.mouser.com/datasheet/2/281/dms-78xxsr-47233.pdf
The $5.00 one I linked earlier is a different device that came out recently. Initially I thought it was the same device I have used, with a new lower price, but it is not. The cheaper newer one actually has better specs than the old one including higher current rating.

So while I can not speak from experience about the new device I can tell you the old $10.00 ones have been in continuous service in several of my personal clocks for >=5 years with no problems. Also, when I first tried one I looked at its output on a scope under no-load and moderate-load conditions. It looked looked clean and fine.

Look into it later when the dust is clearing off the crater.
The following user(s) said Thank You: Pjotrke

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2 years 1 month ago #9101 by Torsten Lang
Hi,
I have some of the RECOM and TRACO POWER regulators in use in my Ackermann ISDN PBX as LDO replacement which - together with some other power supply optimizations - reduced the power requirement by approx. 50%.

Furthermore, I used the TRACO POWER parts as LDO replacement in two transfer table controllers for my model railroad.

The parts in my PBX run 24/7 for several years now without any problems.

With best regards,
Torsten

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2 years 1 month ago #9171 by Pjotrke

Ty_Eeberfest wrote: The Murata buck converters I have used are actually the older (and more expensive: $10.00) ones:
www.mouser.com/datasheet/2/281/dms-78xxsr-47233.pdf
The $5.00 one I linked earlier is a different device that came out recently. Initially I thought it was the same device I have used, with a new lower price, but it is not. The cheaper newer one actually has better specs than the old one including higher current rating.

So while I can not speak from experience about the new device I can tell you the old $10.00 ones have been in continuous service in several of my personal clocks for >=5 years with no problems. Also, when I first tried one I looked at its output on a scope under no-load and moderate-load conditions. It looked looked clean and fine.


Thanks for the suggestion. I've put in the buck regulator that you suggested and it it gave me no trouble.

Except, after starting up the clock I've discovered that the wifi chip gets hot very quickly. This made me doubt myself as I never noticed this with the linear regulator. But after putting the old regulator in the ESP8266 got hot again. The regulator also heated up. Just as noticeable as before. After removing the wifi module, the regulator never got hot again. So it seems to me that the high temps of the 7805 have always been caused by a high current going through the Wifi module.

I haven't been able to get to work on this project due to other matters but any help in solving this case would be appreciated. ;)

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2 years 1 month ago #9184 by Ty_Eeberfest
Just how hot is hot? Are we talking "feels a bit warm" or "I could boil water on the thing"?

I have a Modular here that is bare board (no case) and has been powered on continuously for a few months, so it's clearly all warmed up. The ESP chip feels warm but doesn't burn me. I held a thermometer against it and found it to be 48*C. The room is 23*C, thus the chip is running 25*C above ambient. That is not a problem. Remember, there's a radio transmitting unit inside that time package so it is bound to dissipate a fair amount of heat.

If possible, get a reading of how many milliamps the entire clock is drawing from the external power supply, with and without the ESP module plugged in.

Look into it later when the dust is clearing off the crater.

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