DiSEqC under water

[fulszjep]

Well we had rain today. First time in 145 days. My diseqc seems to be doing well under 3 inches of water. Do you think it will last being under water for a day or so?

 

[7720driver]

What exactly happened?

 

[Mr Tony]

what the heck? Did you have a flood?

The Diseqc shouldn't be under water....Unless its fully sealed, water will get into the connections and screw it up and may fry the receiver

 

[fulszjep]

rain

We had 3 inches of rain fall in a few hours. I thought my dish was going to float away on its stand. I have 2 dishes on stands like sadouns sells. The stands for roof mount. I put the dishes on them due to HOA. I had been getting all the pieces together for my outside metal box to put the switches into. It had not rained in 5 months so I had all the switches just laying on the ground. I had some soggy cables and switches. So I ran all new lines on the outside of the house today.

 

[sharris]

As long as they haven't fried allready. Any electronics can be thouroughly dried and still work. I remember a few years back when someone had a flood in their basement and all of there sat receivers etc.. were completely submerged. He dried them out with a hairdryer over a few days and had no problems with them functioning. I always use pile of silicone around my diseq switches just in case some driving rain/sleet or snow can't get inside.

 

[123tim]

I don't have a Diseqc switch, and have never seen one except in pictures. I was wondering what sort of switching mechanism they use? It would be lucky (for fulszjep) if they were using sealed Mercury-wetted relays. As cheap in price as they are, this probably isn't the case?

 

[mark_calgary]

I don't have a Diseqc switch, and have never seen one except in pictures. I was wondering what sort of switching mechanism they use? It would be lucky (for fulszjep) if they were using sealed Mercury-wetted relays. As cheap in price as they are, this probably isn't the case?

Where I used to work (5 years ago now) we used PIN diodes for RF switching. They are cheap and simple. I don't know what is inside a Diseqc switch as I've never opened one (yet) but wouldn't be surprised to see them there.

 

[Mr Tony]

eh heck I've got a couple old ones at home that the backs are rusted. I'll crack one open and take a picture of it

 

[123tim]

Where I used to work (5 years ago now) we used PIN diodes for RF switching. They are cheap and simple. I don't know what is inside a Diseqc switch as I've never opened one (yet) but wouldn't be surprised to see them there.

Mark,

Thanks,
I had completely forgotten about Pin Diodes. I had to refresh my memory as to what they switched. They do sound like a good candidate. I wonder how the D.C. power switching for the motor and LNB would be accomplished? I guess that the RF could be recombined with the DC after transistor switching the DC?

Thanks again.

A link to a good Pin Diode primer:
http://www.web-ee.com/primers/files/Microsemi/pin.pdf

 

[123tim]

eh heck I've got a couple old ones at home that the backs are rusted. I'll crack one open and take a picture of it

That would be cool.

 

[Mr Tony]

looks like a bunch of resisters and transisters

sorry the pictures arent the best

 

[123tim]

looks like a bunch of resisters and transistors

sorry the pictures aren't the best

Looks like Mark is right. The brownish things right after the input pins of the 75 ohm connectors are diodes. You can see from the traces (my opinion) how it works...the left and right pairs of diodes must have one conducting and one not. They must flip (my opinion again) when signaled, shunting the signal to the opposite connectors. Not what I expected at all.

Pretty cool! Thanks Iceberg!


Are the Pin Diodes switching the DC ( for the motor and LNB) as well as the RF?? It almost looks like they are. I didn't think that this would be possible.

Edit- Most of what I said above is wrong. Please see my next post for the next incorrect statement.

 

[123tim]

Looking at the picture again I see that I was wrong. I see that the switch can switch between four antennas. Only one diode must be switched on at a time. (my opinion once again.)

 

[global0]

C/P from the spec:

"The DiSEqC™ concept is based on extending the present 22 kHz tonesignalling
method, thus minimising the changes required in Tuner-receiver or
Integrated Receiver Decoder (IRD) units, and simplifying backwards
compatibility. However, since the full DiSEqC™ protocol supports a returnsignalling
path and multiple peripheral devices, it is necessary to more closely
define the impedances (at 22 kHz) on the bus, than the simple low impedance
drive (supply voltage modulation) commonly employed with the present tone
method."

Full details/specs can be found here: http://www.eutelsat.com/satellites/4_5_5.html

Thanks all for bringing up the discussion!

Update: I thought that this point was interesting. Again C/P from the spec page at the bottom:

"Important Notice

Level "2.3" is NOT a DiSEqC™ level that has been standardised by Eutelsat. Other DiSEqC™ products may not work correctly with products using this protocol. Please contact the manufacturer of any equipment carrying the non-standard and unapproved DiSEqC 2.3 logo for clarification.

Eutelsat is now considering the best way to incorporate this new protocol (if possible) in to the DiSEqC™ standard to ensure compatibility with all other DiSEqC™ products on the markets."

 

[mark_calgary]

Looking at the picture again I see that I was wrong. I see that the switch can switch between four antennas. Only one diode must be switched on at a time. (my opinion once again.)

Thanks for the picture Iceberg.

Here is what I see:

From each LNB port there is a DC blocking capacitor (brown) then there is a pin diode for each port.

There are 2 more pin diodes that select a left or right side in the centre just above the receiver port .

DC and 22khz are tapped off the receiver port through RF blocking inductors printed on the circuit board (squiggly line patches).

DC and 22khz signals are injected into each LNB port also through a printed inductor (squiggly area just above/below and inside of each LNB connector) and are switched through what are likely transistors (I would use MOSFETS), one for each port.

The rest in the top centre is the disequ command translation logic. (Maybe a little microcontroller?) and some voltage regulation to convert the 13/18V power to whatever the switch requires.


If the switch got wet inside and was turned on it likely wouldn't survive very long but I don't think you would damage anything else.

 

[123tim]

Mark,
Thanks.
I was thinking that the brown components (Caps) were glass diodes with black cathode markings on the ends. I thought the black components (diodes - I assume) were surface mount resistors. This is pretty cool. I think that a new type of forum could be started where a circuit is identified and diagnosed from a picture!
Thanks for the clarification. Thanks for explaining the 22 KHZ tone too. I can see that now.

 

[Mr Tony]

have a few more pictures (thanks to tim who told me to use "macro" on my digital camera

 

[Change]

Properties of PIN diodes...they pass RF when forward biased but block RF when reverse biased.
http://www.radio-electronics.com/info/circuits/diode_simple_attenuator/diode_attenuator.php
http://mrtmag.com/mag/radio_technically_speakingrf_switching/index.html

 

[Tron]

have a few more pictures (thanks to tim who told me to use "macro" on my digital camera

Notice the IC on the board in the upper center area as well. Probably its function is to differentiate between the four tones.

Actually it appears to be a rather complex electronic device when one considers its low cost

 

[Mr Tony]

it looks like everything does run up to that IC when I follow the lines