Apologies and another question

[Del91574]

Nope. Diodes.
 
Have a large campus about 30 min down south from you. I'll do the math. We have a 17 story building with a sub-level. Each level has 2-4 access panels on it, with each having 4 supplies connected (2 for REX power, 2 for lock power). That would put us at a low side of 72 supplies and a high of 144, with the mean being 108 supplies installed in the field.
 
We have a problem with electrified hardware not lasting when we provide voltage within the range listed on them and the manufacturer states the voltage at the handset MUST be 24VDC. Supplies have no provision for voltage output adjustment. Cable runs are within reason for the buildings, really nothing too outrageous and we have 18AWG for the locks. Both the supply manufacturer and lock manufacturer state there is not an issue with their product but the voltage MUST be a tight tolerance and the installed supplies have no provision to do this.
 
About 3 (large) diodes in series drop about 2-3 volts off the supply and don't heat up like a resistor would, not to mention the resistors needed to do this would need an insane wattage.

 

[Del91574]

Pick up the fattest diodes you'd be able to find. The leads are usually around the size of an 18AWG or slightly heavier solid cable and about the diameter of a pencil or slightly larger.Values aren't too important.
 
The Diodes are installed forward biased.

 

[mikefamig]

I like your suggestion for the one big ps in the house and have a couple of questions. What is the adjustable voltage range of that altronix 4amp supply? Will it get me 13.5 - 14 volts at the garage? And why would you need to adjust the voltage with diodes? Can't you just tune the voltage output pot?
 
Mike.

 

[RAL]

Just to expand on DEL's comment about using diodes and not resistors...
 
If you were to use a resistor, the voltage drop across the resistor would vary depending on how much current was being drawn.  The higher the current, the higher the voltage drop, which would cause problems.
 
A diode will have a fixed voltage drop of about 0.7V for each diode. If you need to drop the voltage by about 2 volts, you just put 3 in series.
 
As DEL said, you need to use a heavy duty diode.  They are rated based on the number of amps they can carry.  If your load is 1A, get a diode that is rated at least 2x that.

 

[Del91574]

Yes, you would able to be at the 13-15 range easily with a good battery on the supply.
 
Centralized at the M1, you'd use the diodes to drop the voltage for any peripherals you install and connect to the supply in the house. While most will live and be happy with a higher voltage, some equipment doesn't fare so well with overvolt.
 
A single supply would or could take any device you want to run and loadshed off the M1, allow a good standby time with an appropriately sized battery and still be supervised by the panel via a single zone input. Would also negate any temperature concerns and the necessity for multiple supplies, transformers, batteries (besides the panel and supply).

 

[mikefamig]

Yes, you would able to be at the 13-15 range easily with a good battery on the supply.
 
Centralized at the M1, you'd use the diodes to drop the voltage for any peripherals you install and connect to the supply in the house. While most will live and be happy with a higher voltage, some equipment doesn't fare so well with overvolt.
 
A single supply would or could take any device you want to run and loadshed off the M1, allow a good standby time with an appropriately sized battery and still be supervised by the panel via a single zone input. Would also negate any temperature concerns and the necessity for multiple supplies, transformers, batteries (besides the panel and supply).

 
So there would be one backup battery for the M1 and one for the aux, correct? I can fit that all in my 28" box. I don't want to install another box.
 
Mike.

 

[mikefamig]

Just to expand on DEL's comment about using diodes and not resistors...
 
If you were to use a resistor, the voltage drop across the resistor would vary depending on how much current was being drawn.  The higher the current, the higher the voltage drop, which would cause problems.
 
A diode will have a fixed voltage drop of about 0.7V for each diode. If you need to drop the voltage by about 2 volts, you just put 3 in series.
 
As DEL said, you need to use a heavy duty diode.  They are rated based on the number of amps they can carry.  If your load is 1A, get a diode that is rated at least 2x that.

 
Thanks for the details! I'm sure that I can get them at mouser or allied but I doubt that the local radio shack will have them.

 

[RAL]

If you think you want to go the Altronix route, there are some up for sale on eBay.  This auction has some almost-new AL400ULPD4s for $79.95.   Note that the enclosure is not as deep as the 16-output model DEL linked to, so it can't hold the larger 12Ah batteries like the 16-output model can. Also, it has just 4 fused outputs.

 

[mikefamig]

If you think you want to go the Altronix route, there are some up for sale on eBay.  This auction has some almost-new AL400ULPD4s for $79.95.   Note that the enclosure is not as deep as the 16-output model DEL linked to, so it can't hold the larger 12Ah batteries like the 16-output model can. Also, it has just 4 fused outputs.

Nice price! I would try to fit it all in my 28" elk box.

 

[mikefamig]

This seems like a good time to say that my system has been behaving well for a couple of days now. I've had no control startups and no ethernet restores and no random chimes in a while.Thanks for all the help, I was in over my head and you guys got me there. It's been a learning experience.
 
Mike.

 

[mikefamig]

Depends.
 
If you have the ampacity on a pair to the garage you'd be able to use the trimpot to goose the output voltage up to contend with the voltage drop. To counteract this at the near end to get the output back into spec you would add a few diodes in series with the output to drop the voltage down back to being within spec. If you have distribution boards, you'd have to pre-plan the loads out and which board or point gets the higher voltage vs. the "spec" output or if there's just a single output, it's easy. As an aside, plenty of camera power supplies have 24VAC terminals and 28VAC terminals for just this purpose.
 
It's not as huge of a deal as you think it is. Soldering iron, trip to Radio Shack (hopefully they have the parts) or a decent electronics store, some cable, some solder and shrink tube and it's done and you'd be on a single supply located within the house.

 
The specs on the AL400ULXPD16CB state output voltage 10vdc - 13.2vdc. If it is only 13.2 max then it will be closer to 12.5 volts when it gets to the garage. I was doing better than that with the p212s that measures 13.8vdc at the ps. How will this help? Are you suggesting setting it to 24 volts and then stepping it all of the way down to 13 volts down with diodes?
 
It also calls for 14awg wire on outputs which I completely don't understand.
 
Mike.

 

[mikefamig]

DEL
 
I've been looking at the Altronix web site for an hour trying to select a power supply/charger board with no enclosure and can't find a power supply with a trim pot to regulate the dc output. They all say "electronically regulated output" in the installation instructions including the unit that you recommended. and have no mention of being adjustable. Do you know a bare board that has the trim pot?
 
Mike.
 
EDIT
I've found these two
 

AL400ULXB2

eFlow4NB

 

[mikefamig]

DEL
 
Ignore the two units that I listed in my last post. They are only single output supplies that won't work for me.
 
I did a little reading and learned that the al400ulx is a single output power supply to which you can add distribution boards of different sizes. I don't know if I want 16 outputs as you suggested but might as well go big if I decide to add another box. The thing is that I;d rather not add a second box. The thing is that I don't want to add another box.
 
You said that you have some boards around and I'd be glad to buy one from you if I decide to go this route. Do you have one that has 4 amp output and 4 or more outputs all on one board? Or could I stack the boards on top of each other using double sided tape?
 
Mike.

 

[mikefamig]

Just to expand on DEL's comment about using diodes and not resistors...
 
If you were to use a resistor, the voltage drop across the resistor would vary depending on how much current was being drawn.  The higher the current, the higher the voltage drop, which would cause problems.
 
A diode will have a fixed voltage drop of about 0.7V for each diode. If you need to drop the voltage by about 2 volts, you just put 3 in series.
 
As DEL said, you need to use a heavy duty diode.  They are rated based on the number of amps they can carry.  If your load is 1A, get a diode that is rated at least 2x that.

 
It has occurred to me that you can also use these diodes to act as fuses by choosing the appropriate current rating. Or would that cause too big of a bang when they go off?
 
Mike.

 

[RAL]

Unlike a fuse, you can't really depend on a diode to blow quickly and reliably at the specified current rating.