Mixing pic codes

J

JohnByrne

New member
Apologies if this has been covered but I can't figure out what search words to use.


My old Renard 16 (Xmus) boards use the pic code NOT designed for LEDs. (PMW ?? I forget the terminology but not important). In years past when I needed to drive an LED flood I'd attached a string of AC lights in the circuit so it will latch. I want to get away from that. I know I can flash PIC chips and change them all out but I hate fixing things that are not broken and I only need LED capability on a couple of boards, not all 8 of them. The question is can I mix the PIC codes or do all Renard boards in the daisy chain need to use the same PIC code? One step further, a Renard 16 board utilizes 2 PIC chips each driving 8 SSRs. Can I mix code versions on the single boards? My goal is to limit how many PIC chips I'll need to flash and change out.

I know I could flash chips and test but honestly being a Mechanical Engineer, when I get to board level it makes me nervous and I'd love to not touch something that works.

Thank you very much in advance
John
 
You're fine to mix and match the pwm settings as long as all the pics are using the same baud rate. The same should go for mixing and matching on a single board but I would switch the full board with the pwm configuration while you have that board open. I personally use the pwm configuration on all my Renards to avoid any issues.
 
Thank you much. Yeah I wish I had used the PWM originally but that was 2007 lol. I've slept since then so not sure why I didn't other than maybe thinking I'd reduce power consumption a bit. Thank you again.
 
I think your issue is the Triacs on your old boards. When we switched to LED's, we found that the original Triacs would not latch with the lower current draw. Some folks started using 'snubbers', and some folks swapped out the original Triacs for newer more sensitive ones. It has been too long for me to remember part numbers, hopefully someone more familiar with them will chime in with that infol.
 
using non pwm, you reduce power consumed in the circuit that drives the triac. saves you a fraction of a penney over the entire show season.
 
I don't recall hearing any issues with using the original triacs with the PWM code and led floods. If however this is the case I'm not going to unsolder and replace the triacs so no need for anyone to research a part number :). I'll just add a load via a string of lights. I used the controllers 5 or 6 times in a rather large local haunted house and that's what I did to create the lightning effects in the grave yard scenes. 5 or 6 LED floods flickering in the right order with 4 channel sound and about 600 watts makes for some amazingly convincing lighting lol.

Yeah, if it doesn't work I'll just hang a bundle AC lights in parallel so I have a work a round. :)
 
JohnByrne said:
I don't recall hearing any issues with using the original triacs with the PWM code and led floods. If however this is the case I'm not going to unsolder and replace the triacs so no need for anyone to research a part number :). I'll just add a load via a string of lights. I used the controllers 5 or 6 times in a rather large local haunted house and that's what I did to create the lightning effects in the grave yard scenes. 5 or 6 LED floods flickering in the right order with 4 channel sound and about 600 watts makes for some amazingly convincing lighting lol.

Yeah, if it doesn't work I'll just hang a bundle AC lights in parallel so I have a work a round. :)
Click to expand...
no need to swap triacs when using pwm.
 
That was my understanding too. I have 3 PICS in hand so my plan is to flash them and give it a try. I only need 3 for this next show plan. Thank you all! As always, the help is very appreciated.
 
I was fortunate enough to have built some of the very first renard boards. That was a long time ago so I had to refresh my memory. There were 2 firmware versions. PWM and non-PWM. The latter is what I have flashed which is why LEDs don't latch. It has nothing to do with the triacs I'm 99.9% sure of. What I wasn't sure is if I could mix the versions which I now know is possible as long as each is setup for the same baud com rate. Lol it's coming back to me now ha ha. 2007 was a long time ago
 
non-pwm does dimming by sending a single fixed width pulse to the triac at a point in the AC cycle that will give the desired output intensity. This method counts on the triacs ability to latch and stay on when the pulse goes away. If you are really early in the AC cycle (>80% intensity) or really late in the AC cycle (<30% intensity) there may not be enough current flow through the triac to cause it to latch on. Adding a resistive load (aka snubber) would increase the minimum current drawn by the string and allow the triac to latch. Switching to a triac with a lower latching current helped extend the useful range of dimming.

PWM mode sends a variable length pulse that starts at some point in the AC cycle and stays on until just before the zero crossing point is reached. In this way, the controller does not care what the latching current requirements are in the triac. The triac is actively driven by the controller for the entire time it is supposed to be "on". As you can imagine, this causes more wear on the opto isolator LED used to drive the triac and draws a few mA more current from the controller PSU. On a device designed for continuous 'on' operation of 20 years or more, you would not need to replace an moc due to PWM within your lifetime (or your kid's lifetime).

Since we buy electricity at a rate of 0.70USD / Kilo Watt hour, the increase of current by even 5ma to the moc costs you:

cost per watt = 0.70 [KWH] / (1000 = 0.0007 USD/Watt
watts per triac opto = I * E = 0.005A * 5V = 0.025W
cost per channel at 100% brightness to drive the triac for 1 hour = 0.0007 * 0.025 = 0.0000175USD/hour

For the non-pwm mode you would divide that cost by your line frequency (60hz USA) = 0.0000175 / 60 = 2.916666666666667e-7 USD per hour at 100% intensity.

The place where the power used per channel gets more expensive is when you have an additional indicator light per channel. The extra current for those indicators will not cost you a lot of money to run (Add 20mA / channel) but it does have an impact on the controller PSU. That PSU now needs to supply that extra current. With todays large PSUs, this does not matter. However, my ren64 has 64 indicators and that will have an impact on the size of transformer and regulator chosen, which increases the cost of building the controller.

The point here is that if the PSU on your controller has the capacity to provide the extra current to drive the moc device then there is no real reason to use non-pwm and it is VERY likely that your controller will have the needed capacity to drive the moc using PWM (nobody cuts their design so close that a mA or two added load is going to cause an issue.
 
If you do have flicker issues after switching you can always add a resistor to all the outputs. Or just the outputs that are having issues. I did this on mine just in case. It's not pretty with the xmus boards but with some wire and some wago connectors it's doable.
 
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