design suggestion to improve user safety.

[scorpia]

RJ,

i was looking over the express board and i came across something which i think could be improved on to help increase the safety of the design .

i was looking at the position of the current limiting resistors for the led indicators. I think it would be a safer design to move them from the high voltage side of the opto's to the low voltage side.

This would inprove the minimum seperation between the 2 sides from about 1mm to 6mm.

With the current design it wouldnt be hard to get a solder bridge between the top of the resistor and pin 6 of the MOC creating a short from the mains voltage to the logic side of the board.

being that you have another coop on the way now would probably be a good time to do the redesign.

regards

Peter

[RJ]

Thanks for the recommendation,

 I do not think I want to make that big of a change but I will look at moving the optos and LED's up a little to open up the distence to far enough that a bridge would be extremely hard to make on solder mask. This should give it plenty of margin for someone hows soldering is less than good.  It will not be on the next coop as I already have more than enough PCB's to fill the coop. It will need to wait till near the end of the year if we run another coop then.

RJ

[scorpia]

Moving the Opto does help the 2 solder points near the top of the resistor but leaving the resistor in place where it is still leaves a gap of about 1mm between the bottom of the resistor and the main Trace for the Triac power.
Im sure it wouldn’t take much of a spike on the mains voltage to spark across a 1-2mm gap. particularly on a damp winters night when the rain or snow is falling.

The whole idea of having the resistor on that side of the opto’s might make the design "look good" but I don’t think it was a wise choice to make considering the potential dangers from such a move.

i would have thought that as a general rule everyone would put personal safety above aesthetics.

reading up across the net a generally accepted standard found on multiple websites for mains traces and the isolated signals would be about a 8mm gap. 
Im sure you would agree that mixing the mains signals and the isolated signals on any board is a bad choice if it is possible not to do so easily.

[rrowan]

Moving the Opto does help the 2 solder points near the top of the resistor but leaving the resistor in place where it is still leaves a gap of about 1mm between the bottom of the resistor and the main Trace for the Triac power.
Im sure it wouldn’t take much of a spike on the mains voltage to spark across a 1-2mm gap. particularly on a damp winters night when the rain or snow is falling.

The whole idea of having the resistor on that side of the opto’s might make the design "look good" but I don’t think it was a wise choice to make considering the potential dangers from such a move.

i would have thought that someone as yourself would put personal safety above aesthetics.

reading up across the net a generally accepted standard found on multiple websites for mains traces and the isolated signals would be about a 8mm gap. 
Im sure you would agree that mixing the mains signals and the isolated signals on any board is a bad choice if it is possible not to do so easily.

You comments are bit over the top. Was this done on purpose?

Rick R.

[scorpia]

sorry it was not meant to be over the top. i am not trying to offend anyone. 

I just think this is an issue that needs to be resolved and in my personal opinion moving the opto up a bit wont fix the issue.

but it is just my personal opinion. something which i thought we were allowed to share. i have edited what i thought you could have taken the to be over the top.

[rrowan]

sorry it was not meant to be over the top. i am not trying to offend anyone. 

I just think this is an issue that needs to be resolved and in my personal opinion moving the opto up a bit wont fix the issue.

but it is just my personal opinion. something which i thought we were allowed to share.

So this statement was not trying to offend anyone?

i would have thought that someone as yourself would put personal safety above aesthetics.

Rj said he would take a look and move thing around to make it safer and then your second post was an attack. Opinions are allowed what is NOT allowed is personal attacks.

Rick R.

[scorpia]

please check my edit. and no it was not meant as an attack.

note that the edit was done before you post was made

[RJ]

I think this is quite enough!
This is sounding more like an insult because I do not agree.

There is more to the required spaceing than just the distence between something and the operating voltage. The opto should be moved to give more clearance and will be the next time the pcb is updated for an additional margin of safety. The resistors will not be moved to the otherside.  This has nothing to do with aesthetics.

RJ

[RJ]

Ok to do constructive work with the information pointed out I intended to move the Opto's up and gain clearence. If you look at the first picture the issue is that the two points in location A are too close together. One is low voltage and the other is high voltage. Not sure how I missed this.  Make sure when you solder these you do not bridge them so check them over well.

The location B is the pin and trace that is completely covered with epoxy. This should be no issue as there is nothing exposed to short. I planned to add a small amount of space here with the move also

The funny thing is while I was moving the Opto a thought came to me. And with some quick math I found that if the LED and the opto was put in series neither one would have a need for a current limiting resistor.

I took a ver 2 Express and removed 32 resistors include all the 330 ohm and half the 180 ohm. Jumper the board for testing and found this to be correct. Both devices got perfect current and voltage with this arrangement.

The second pictures shows a new version 4 PCB for the express with these changes. IT drops 64 solder joints and 64 leads to bend. It reduces the part count by 32 items.

This will speed building. I will need to have pcb's made for the coop as I did not have as many left as I thought and do not have enough to fill the coop. So the new PCB's will be on the current Express Coop #4.

I Also added a jumper to allow you to switch between wired and wireless without removing the RS485 chip.

The new Lynx PCB logo will replace the Vixen logo from here out also.

The second picture is the new layout without all the resistors. This is a change on the pcb so you will need to install the resistors on all current boards. The Ver 4 is the only PCB that does not need them.

This post changes nothing for anyone other than to check the location pointed out to make sure you have no solder bridges before you power up your Express.

RJ

[cmorda]

Nice work RJ!

Running the opto and LED in series is very innovate.

Thanks!

Chris

[ThaiWay]

RJ...  so for 240V operation the remaining 180 Ohm resistors would be replaced by 330 Ohm for Ver 4 PCB? 

Just checking

John

[RJ]

RJ...  so for 240V operation the remaining 180 Ohm resistors would be replaced by 330 Ohm for Ver 4 PCB? 

Just checking

John

Yes just as before this will not be effected by the change.

We are just useing the LED to be the resistor for the Opto and the Opto to be the resistor for the LED. Thus eliminating 32 resistors.  Current works out to exactly 5ma which is what we want. both leds add up to 3.3 volts so we come out perfect due to the 3.3v nature of the expresses logic circuit.  A shorted led will not damage the opto as it is rated for 50ma max and the pic only delievers 45ma with the led shorted.  A failed Led just prevent the channel it is on from operating so no problem there you would just change it out. (how often do we kill indicator leds running them at 5ma?).

RJ

[jnealand]

Anytime this newbie reads about less soldering and parts I think it is great.  I don't have a clue as to what these design decisions mean, but as long as it works and I can follow your assembly instructions I'm good.  Thanks.

[lonewolf41]

Anytime this newbie reads about less soldering and parts I think it is great.  I don't have a clue as to what these design decisions mean, but as long as it works and I can follow your assembly instructions I'm good.  Thanks.

Boy, I am with you!!  So did I understand you (RJ) to say that the PCB's for the current 4th LE coop will be this version 4?  These LE's will be my first so less stuff to solder is way OK with me. 

Thanks for the work RJ,
-Keith

[RJ]

Anytime this newbie reads about less soldering and parts I think it is great.  I don't have a clue as to what these design decisions mean, but as long as it works and I can follow your assembly instructions I'm good.  Thanks.

Your Good!

RJ