5v Voltage regulator and extreme temperatures (need suggestions)

[brandonj]

It looks like the 5V voltage regulator may not like extremely cold temperatures.   Here's a little background of my situation:

I am in Salt Lake City, UT.  and we are looking at about 15F degrees or so at night.  When turning everything on last night, all my LE's that were powered down would not power up when I turned them on.  The 3.3v LED was lit, but everything else was dead.  3 out of 5 of my LE's were this way. The other two that were working, were powered on all day long.

So, I took one inside to troubleshoot, and within a minute or so, it powered on as normal and everything worked.   I went out side and tried to warm up the 5V regulator on the other LE's with my hands, and what do you know, they started working.  It seems that it doesn't take much heat to get them working again, but it does look like it doesn't like the cold all that much either.  So here's my question:

What would you recommend to use to keep the inside of the box a little warmer, so I don't have this problem?  I thought about using a little 20 watt bulb or something, but I wonder if theres something out there that is a little more effective and safe.  I don't want to be heating it up all that much - just enough to keep it working.

Ideas?

-Brandon

[David_AVD]

The L7805AB regulator specified in the kit seems to be rated down to -40 degrees Celsius (-40F) so should be ok with -10C (15F).

The L7805AC is only rated down to zero C (32F). Maybe check which one is actually fitted to your unit?

[brandonj]

Hmm.. I got the parts from a co-op, so I would hope it is the correct part, but I will check on that.  It certainly seems to have the limit of the "C" part though, so you very well could be right.

[RJ]

If the 5v reg is not putting out you should not have 3.3 volts?  unless this is one of the modded units. David is correct the correct part for the unit should be good to -40 so it should not be an issue.

RJ

[WWNF911]

Last couple of nights I have had this isue as well.

I don't remember which is which but only the top power LED on the left lights up. Verified today that if I applied power to the controller before the temp went down the LE would power up normally. Last couple of nights have been cold. Night before last -8 and last night -5. Interestingly enough the 2 controllers for the arches were down night before last. Last night 3 out of four LE's working in the yard were down. Tonight powered up like I said before the temp went down, crossed my fingers and went back to work. 

More at eleven... 

[brandonj]

If the 5v reg is not putting out you should not have 3.3 volts?  unless this is one of the modded units. David is correct the correct part for the unit should be good to -40 so it should not be an issue.

RJ

I _think_ it's a V2 board, but I can't remember for sure - I got them in a coop around january of this year.

[RJ]

Could it be the 3.3 v not coming on. Looks like the reg for it is rated to 0c ?

RJ

[OkieJay]

Could it be the 3.3 v not coming on. Looks like the reg for it is rated to 0c ?

RJ

On mine, the 3.3 was not lit, when I first powered up tonight.  I took it inside and it lit up as soon as I plugged it back in.
It is working fine right now (-8 C outside).  Mine is a version 3 from a coop this spring.

Jay

[mschell]

I haven't seen any issues with my 4 LE's yet.  However, we haven't had that much cold weather yet.  Been down to freezing (32F) one or twice, but we'll probably see a test of 15-20F in the next day or so.

My approach is to leave the controllers with power applied 24x7.  That way most of the electronics stay warm, less chance of condensation from morning dew, etc..   The controllers don't take much power when the lights aren't on, so it's not that much of a green issue.

I've been doing it this way for the last 5 years, and with 19 AL controllers and now 4 LE's and 2 SSR4's added to the bunch it seems to work fine.

[OkieJay]

Happened again tonight, no light on the 3.3 LED and no activity.  Closed the cover and went inside to get hair dryer.  By the time I got back outside it was working.  Only having problem on one of my two Expresses.  The one mounted to my junior megatree has not had a problem, but a little sun is usually still on it when we turn on the power.  The other Express is under a plastic tub behind some bushes, so it gets no sun to warm it.  I definity think the cold is the factor.  Current temp here is -1 C.

Jay

[blickensderfer]

Jay,

I had one do the same as yours.  The temp in Ohio is 22 F and the 5V led was on but the 3.3V led was not.  After about 5 mins, it must of got warm enough to start.

I took a C7 bulb and placed it right above the 5 & 3.3 heatsinks and zip tied the plastic socket to keep it in place.  I directly wired the bulb to the left side main power cord to keep it on 24/7.  I'll see if that works and let you know.

Dan

[RJ]

The 3.3 v reg is only rated to 32 deg f and I guess they do not make this model in units rated for colder. If you turn them on and leave them on for a few minutes they are coming on after the reg warms itself up. Or you can grab the bottom regs heatsink with you fingers with no gloves and they will warm up. I have already changed the part out on the pcb to accept a different 3.3 reg with a different pin out for future boards that is rated to -40c like the rest of the parts I also added resistors across the output to act a snubbers for the leds. this seems to be a common issue with all the controllers including LOR and the leds. Instead of adding them as plugs you make up it is easier and cheaper for me to add them to the pcb. Will help led users and will not hurt incidence users. This will be on the express version 5 pcbs starting with the next coop.

I attached a image of the layout for the ver5 express pcb.

RJ

[WWNF911]

Thanks for the hard work RJ. I don't however want to toss my version 3's aside. 

Is it possible to modifiy our older version boards with the newer regulator/ more temp forgiving parts?

[David_AVD]

How about the LM3940T-3.3

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[RJ]

Thanks for the hard work RJ. I don't however want to toss my version 3's aside. 

Is it possible to modifiy our older version boards with the newer regulator/ more temp forgiving parts?

Yes the LM3940T-3.3 david is pointed at can replace the 3.3 regulator to fix it on current pcbs. I do not mean for you to throw away your current pcbs just looking at improving newer ones.

The  LM3940T-3.3 is not avaliable from mouser so I am not using it on the new pcbs.

RJ