Can Sunlight Crash a Cable Box? - Page 1
Forum section: electronics / general

author: xrunner
author_rank: Super Contributor
timestamp: April 21, 2013, 12:01:37 am
content: Had to get three new cable boxes several days ago. This due to a grand new plan by the local cable Co. to screw us for more money (that's another story though).One of the cable boxes, because of the time of year, gets swept with light by the setting sun in the evening with light coming in through the patio door. Last night when this happened it seemed to cause it - to use a technical term - freak out. It sent crazy green/white/black lines to my HDTV and I couldn't turn it off with the remote (yes I know the sunlight was probably swamping the IR remote). I went and turned it off with the physical button and it re-booted, and for the rest of the evening was just fine. Was this due to the sun or a bad box?Tonight it happened again. I watched TV for 30 min and when the sun swept it it got zonked out again. This is too much of a coincidence isn't it? I know I can close the blinds but how can this happen? Wouldn't the logic of the IR input only allow pre-programmed actions to occur?

author: Skimask
author_rank: Super Contributor
timestamp: April 21, 2013, 12:35:33 am
content: How about the heat from the sun overheating some of the components and causing the problems? vs. any IR induced malfunctions or stray neutrinos....

author: IanB
author_rank: Super Contributor
timestamp: April 21, 2013, 12:38:56 am
content: I'd guess the IR content of the sunlight overloaded the input sensor and caused it to go phooey. Don't let the sunlight shine directly on it...

author: xrunner
author_rank: Super Contributor
timestamp: April 21, 2013, 12:41:08 am
content: Quote from: Skimask on April 21, 2013, 12:35:33 amI wouldn't think so - the light isn't on it long enough to heat it up. It's already warm anyway because it's not ever really off. That's one beef I have with these boxes. They are silent energy hogs. The one I turned in (Scientific Atlanta) was even worse. It was approachingverywarm even when off all night. These new ones are Cisco and at least they are not as warm.

author: chickenHeadKnob
author_rank: Super Contributor
timestamp: April 21, 2013, 02:02:33 am
content: Quote from: xrunner on April 21, 2013, 12:41:08 amThis was my first guess as well, don't just dismiss it as I can see a plausible mechanism. The sunlight hits the box, the outside shell (probably black plastic) heats up and expands. This puts mechanical strain on a connector or cold solder joint. Even if the inside of the box is at near thermal equilibrium because it has been running, and you are right they are hogs, the differential strain caused by the expanding shell can make things wonky. Just a wild ass guess.You can eliminate the ir port from consideration by covering it up with opaque tape and leaving the box in position. good hunting.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: April 21, 2013, 08:09:12 am
content: It's possible that sun on the remote sensor could cause it to output something the software isn't expecting - e.g. oscillating and saturating it with interrupts, but I think temperature rise is probably a more plausible explanation. These things run pretty warm,and are engineered down to the minimum possible cost, so there won't be much additional margin for tolerance to external heat sources.You could easily determine which using some foil tape over the sensor - needs to be foil as paper and many other opaque materials are quite transparent at IR.

author: xrunner
author_rank: Super Contributor
timestamp: April 21, 2013, 01:25:42 pm
content: Quote from: mikeselectricstuff on April 21, 2013, 08:09:12 amI turned on the system for over 30 min this morning and it didn't "freak out".I have the same exact box in front of me on my computer desk (it's one of the three I got). I used a small flashlight to find what I thought was the IR window, but when I covered it with my hand it still received commands from the remote. I put my arm across the front panel and it still got the signal. I put two junk mail envelopes that were thick with several layers of paper inside - still got it. Added two pieces of cardboard behind those - still got itWow. I can't believe it's that sensitive. Problem now is I don't think I can block the sensor without blocking the whole box, but then that's basically like closing the vertical blinds at the patio door.Attached pics. The pen is pointing to what I believe is the IR sensor window.

author: SeanB
author_rank: Super Contributor
timestamp: April 21, 2013, 01:41:43 pm
content: Could the remote not be a RF link? Often these decoders are put in a cupboard or furniture, and the RF link works through the closed door. There could be a IR link for programming on the board that is being swamped.

author: xrunner
author_rank: Super Contributor
timestamp: April 21, 2013, 01:44:19 pm
content: Quote from: SeanB on April 21, 2013, 01:41:43 pmNo it's not RF. If I hold the remote under the table it stops the signal. I just never imagined the receiver would be so sensitive. It's incredible! I guess you don't want consumers complaining about their equipment not working with the remote, but I think this is ridiculous.

author: wb3fsr
author_rank: Contributor
timestamp: April 21, 2013, 02:37:16 pm
content: Lets try a couple of additional tests.First try to shield the remote front end with the palm of your hand - Are you still able to command the CBox with the remote covered?Many cable box remotes use dual emitters and the signal can bounce off reflective surfaces rather well.Once we have fully ruled out ir reflection, you may find that you do indeed have a dual mode remote with both RF and IR...Using a table to block the remote may also provide sufficient loss to block a very low power RF signal as well.Either you should be able to narrow down the IR rx sensor location or find your dealing with an RF capable remote.As for the actual stated problem, I would lean towards heat rise. Try a hair dryer on the CBox to see if you can duplicate the issue.RegardsPeterV

author: xrunner
author_rank: Super Contributor
timestamp: April 21, 2013, 02:54:29 pm
content: Quote from: wb3fsr on April 21, 2013, 02:37:16 pmYep! Seem to go right through my palm.QuoteNo dual emitters. It only has the front window and I can see one IR LED.QuoteNo it isn't RF. If it's under the table right next to the box it won't work.I even covered the front of the remote with a shoe box lid and it still works. If I block it with a metal can it won't work.

author: PA0PBZ
author_rank: Super Contributor
timestamp: April 21, 2013, 06:15:33 pm
content: Quote from: xrunner on April 21, 2013, 02:54:29 pmWell, there you go. Put the metal can in front of what you think is the IR receiver and test again.

author: xrunner
author_rank: Super Contributor
timestamp: April 21, 2013, 06:55:42 pm
content: Quote from: PA0PBZ on April 21, 2013, 06:15:33 pmIt doesn't block it that way, I just tried it. If I cover the remote completely by putting the whole front of it inside a metal can, the signal is blocked.If I put the metal can in front of the IR detector on the box and hold the remote at the usual distance, it still sees the signal. There is leakage of the signal into the detector from reflections I suppose. Reflections off the can, into the room, back into the plastic around the panel - the whole front panel is clearish plastic. I mean I can put tin foil over the whole damn panel and block it, but then it won't tell me if it's heat or blockage of just the IR signal.It's just so sensitive - far more sensitive than I would have thought possible.

author: PA0PBZ
author_rank: Super Contributor
timestamp: April 21, 2013, 07:10:07 pm
content: Could it be that it has 2 sensors?Take it apart and disconnect the sensor

author: mikes
author_rank: Regular Contributor
timestamp: April 21, 2013, 07:35:27 pm
content: Wrap the box in aluminum foil, then "unwrap" one side at a time (back, bottom, top, sides, front). See when it starts working.

author: ddavidebor
author_rank: Super Contributor
timestamp: April 21, 2013, 07:43:30 pm
content: Quote from: mikes on April 21, 2013, 07:35:27 pm+1

author: xrunner
author_rank: Super Contributor
timestamp: April 21, 2013, 09:30:07 pm
content: Quote from: PA0PBZ on April 21, 2013, 07:10:07 pmLOL - not only does it have security screws, it has a nasty lookiing Orange sticker seal that has words like "Federal crime", "Jail", "Property of Cable Company", "Tampering", ... no, I won't be taking it apart.You know those ancient Indian ruins that have stones arranged where the sun only shines through twice a year? That's what this is like. In a few more days it won't be a problem. I can close the blinds, I just thought it was interesting that the sunlight would do this to it. It's cloudy today anyway.

author: amyk
author_rank: Super Contributor
timestamp: April 22, 2013, 10:17:07 am
content: Quote from: xrunner on April 21, 2013, 02:54:29 pmThis really sounds like RF to me; when it's under the box, the bottom of it being a big grounded metal case probably blocks the signal.You can try shining "artificial sunlight" at the box, with a suitable incandescent lamp.

author: xrunner
author_rank: Super Contributor
timestamp: April 22, 2013, 11:15:54 am
content: Something else is going on. It did it again last night about the same time, and it was cloudy.Remember in the morning I ran it for over 30 minutes and it was fine. But at about the same time, when I go to watch TV in the evening, it zonks out once in about 10 minutes, I re-boot it, and for theentirerest of the evening it works without issues.

author: cwalex
author_rank: Frequent Contributor
timestamp: April 22, 2013, 11:27:14 am
content: Quote from: xrunner on April 22, 2013, 11:15:54 amIf you have 3 of these boxes in your house why don't you swap the troublesome one with one of the others and see if the problem is with that particular box or the environment?

author: xrunner
author_rank: Super Contributor
timestamp: April 22, 2013, 05:28:33 pm
content: Quote from: cwalex on April 22, 2013, 11:27:14 amThat's certainly a logical step. I want to leave it there for a few more days, then either swap it or just take it back to the cable company for another new one.

author: rsjsouza
author_rank: Super Contributor
timestamp: April 22, 2013, 05:50:21 pm
content: For a short period of time (2 months, back in 2010) we had Dish (there, I said it) and the receiver was, to say one of Dave's faves, an "utter pile of turd".Among a pile of issues, the most annoying was an interference between the TV's automatic bright/contrast/color feature and the IR sensor on the set top box (a few threadshereandhere). I had several of the symptoms reported and turning off the auto-bright and the power saving features of the TV turned the remote control usable again.Obviously that this may not explain why the functions jump around in your STB, but surely the sunlight will influence the TV's autosettings.

author: SeanB
author_rank: Super Contributor
timestamp: April 22, 2013, 08:05:35 pm
content: Older decoders here for pay TV also have an issue of changing channels randomly when you use the TV remote. Solved that one with some black tape over the sensor, and use the button on the unit to cycle through the channels if needed, but there are only 2 that are needed. Problem was solved sort of by the introduction of satellite receivers that brought in a whole new set of problems.

author: JackOfVA
author_rank: Unknown
timestamp: April 22, 2013, 08:32:15 pm
content: IR codes are transmitted as on/off keying, and the photo diode is AC coupled to a comparator with one path being via a long term (long with respect to the data burst period) average of the photo diode output and the other being the data burst filtered only enough to take the edges off but to keep the data intact.The data rate varies depending on the particular manufacturer, but 30-40 KHz is the normal range.The long term output represents an average of ambient light and hence provides a sliding reference against which the IR on/off signaling can be read. In other words, the remote control IR signal is compared to the average ambient light to determine if the IR signal is on or off.When the photo diode is exposed to strong external IR radiation, such as from sunlight striking the sensor, it will eventually saturate or at the least go into a non-linear range where the desired IR signal is such a small increase with respect to the ambient that it no longer can be properly decoded.While IR filtering via an appropriate color plastic helps a lot - since it keeps the IR detector from being saturated with visible light - there's a limit to how much selectivity the optical filter has, particularly in an inexpensive consumer product.Scope shot below is a typical output of an IR decoder module. This is from Chapter 22 of my book "Programming the PIC Microcontroller with MBASIC" at which you can read more than you ever care to know about how to decode an IR remote control signal with a PIC and MBASIC.

author: xrunner
author_rank: Super Contributor
timestamp: April 22, 2013, 11:09:38 pm
content: Thanks Jack.Does the seemingly extreme sensitivity of this system to it's transmitter (the remote) surprise you? If you don't know what I mean read back a few posts. To me it's amazing that the receiver can get a signal after the many ways I've tried to block it.

author: JackOfVA
author_rank: Unknown
timestamp: April 23, 2013, 12:53:03 am
content: Quote from: xrunner on April 22, 2013, 11:09:38 pmNo it does not surprise me. A good IR sensor will read signals bounced off walls, ceilings, etc. Some TV sets will also have multiple IR sensors physically separated and looking in different directions with the thought that if one is blocked, a different sensor will detect the signal. Don't know if that's the case in your cable box or not, though.By the way, if you wish to determine if your control is really sending IR or it's RF, look at the emitting end of the remote control unit with a digital camera. Most digital cameras are sensitive into the near IR and the remote control IR output can easily be seen in the digital camera monitor. (You should hold down a function button, of course, so the remote controller emits a more or less continuous string of IR messages.) This won't work with an SLR type camera as you are looking through the lens, so you need one that displays the image on the built in monitor.

author: xrunner
author_rank: Super Contributor
timestamp: April 23, 2013, 02:12:28 am
content: Quote from: JackOfVA on April 23, 2013, 12:53:03 amYea it's IR alright. I can see it in my camcorder and also with a piece of IR detection paper.What modern consumer A/V equipment uses RF these days?

author: PA0PBZ
author_rank: Super Contributor
timestamp: April 23, 2013, 07:13:49 am
content: Quote from: xrunner on April 23, 2013, 02:12:28 amI have a Sony Android box that has a keyboard one one side of the remote. That uses RF because it is hard to type and point at the same time.