Selecting a 12VDC solution

[cglaeser 0]

I have an Altronix 24VAC power supply and want to power several Crow D&D PIRs. The Crow input is voltage is between 7.8-16VDC. I am considering the Altronix AL624 and VR1 as possible solutions. The specs are as follows:

 

The Altronix AL624 power supply/charger converts 24VAC input to a 1.2 amp of continuous supply current @ 6VDC or 12VDC or .75 amp of continuous supply current @ 24VDC.

 

The Altronix VR1 converts a 24VAC or 24VDC input into a regulated 12VDC @ 1 amp output.

 

I assume that one major difference is the VR1 is regulated, is that correct? Given that the D&D permits a very wide range of input voltage, will either solution work fine? Are there any other considerations?

 

Best,

Christopher

[mike_va 0]

I assume that one major difference is the VR1 is regulated, is that correct? Given that the D&D permits a very wide range of input voltage, will either solution work fine? Are there any other considerations?

 

The other one looks regulated also, with a simple 3 terminal linear reg? Hard to tell about the VR1, because it is in a box. Will they send you schematics?

 

How much current do the PIR's take? As long as they are fairly low (<100mA total) I would go with the linear reg.

 

Assuming just a simple linear reg doing some rough number crunching, 24VAC rectified will be less than 36VDC (I'm being lazy with the math) and at 100mA this would be (36-12)*0.1=2.4Watts on that heatsink which is probably around 20C/W or something like that so you should be fine. Try it out when you get it, if you can touch the heatsink it is less than 50C (call it a rule of thumb...).

 

If you think you are going to need more current I'd call them and ask if the other is a switcher.

 

The other (unlikely) issue would be ground loops, I'm not familiar with those PIR's but if relay contact outputs (i.e. isolated) like my Honeywell's should not be a problem.

 

Have not spent alot of time looking at this but hope this helps.

 

Mike

[cglaeser 0]

How much current do the PIR's take? As long as they are fairly low (<100mA total) I would go with the linear reg.

Very modest current at 8.4mA per PIR. Which one is the linear reg? The AL624?

 

The other (unlikely) issue would be ground loops, I'm not familiar with those PIR's but if relay contact outputs (i.e. isolated) like my Honeywell's should not be a problem.

Yes, I think they are isolated relays. Thanks for the assistance.

 

Best,

Christopher

[mike_va 0]

The AL624 looks like a linear reg. The other one I can't tell.

 

The only other thing I'll mention is that I tried using PIR outdoors using an indoor Honeywell PIR. Did not work at all. They must have different sensitivities or something for the outdoor models.

 

P.S. There is a company in England that sells inexpensive kits, PM me and I can send you a link I don't think I'm allowed to post that. The nice thing is they also provide all schematics. Perhaps not quite as inexpensive as the one you've found, I've built a few of their kits with good results.

[cglaeser 0]

The only other thing I'll mention is that I tried using PIR outdoors using an indoor Honeywell PIR. Did not work at all. They must have different sensitivities or something for the outdoor models.

Good point. Optex and Crow make excellent outdoor PIRs. I am currently using the Optex Redwall SIP-100 to monitor a footpath that is 100 meters from my house. That PIR is an incredible performer, rain or shine. I have not yet used the Crow D&D, but it too receives excellent reviews.

 

P.S. There is a company in England that sells inexpensive kits, PM me and I can send you a link I don't think I'm allowed to post that. The nice thing is they also provide all schematics. Perhaps not quite as inexpensive as the one you've found, I've built a few of their kits with good results.

Thanks, will do.

 

Best,

Christopher

[bpzle 0]

Just put in a few Vertiline series... Rackmount 1u. Makes for a pretty slick install.

[Soundy 1]

I use the Labco regulator boards all the time - both the PS241F (http://www.electronicproductonline.com/catalog/product_info.php?products_id=2237) and the PS243F (http://www.electronicproductonline.com/catalog/product_info.php?products_id=1770 - sorry for the store links, it's the only listing I could find for them; Labco doesn't appear to have a website of their own). They fit nicely inside Pelco, Altronix, Honeywell, Enforcer, and most other power cans - tie the input into one of the 24VAC and channels and away you go.

[cglaeser 0]

Another question about voltage regulators. The AL624 has jumpers to select the output voltage of 6VDC, 12VDC, or 24VDC. The suggested input voltages are the following:

 

12VAC input for 6VDC output

16.5VAC input for 12VDC output

24VAC input for 24VDC output

 

Given that 24VAC is already available, rather than use a 16.5VAC wall wart, is it OK to use 24VAC input for 12VDC output? Do voltage regulators dump the excess voltage as heat? Will using 24VAC produce more heat than 16.5VAC when the output is 12VDC?

 

Specifications are at http://www.altronix.com/p_pdf/AL624.pdf

 

Best,

Christopher

 

Edit: Wiki is my friend: Unlike a linear power supply, the pass transistor of a switching mode supply switches very quickly (typically between 50 kHz and 1 MHz) between full-on and full-off states, which minimizes wasted energy. Voltage regulation is provided by varying the ratio of on to off time. In contrast, a linear power supply must dissipate the excess voltage to regulate the output. This higher efficiency is the chief advantage of a switch-mode power supply.

[cglaeser 0]

The AL624 looks like a linear reg. The other one I can't tell.

 

I can't find a description of the implementation for the VR series. Given that the VR1 through VR5 series are packaged in a relatively small plastic box without a large exposed heat sink, is it likely that they are the more efficient switching regulators? The VR4T converts 24VDC to 12VDC @ 3A. Wouldn't a linear regulator require a relatively large exposed heat sink?

 

See http://www.altronix.com/index.php?pid=2&model_num=VR4T

 

Best,

Christopher

[mike_va 0]

Wouldn't a linear regulator require a relatively large exposed heat sink?

 

Yes, that is 36W it has to get rid of if it is a linear reg. There is a possibility they are just rating the current capability though, not power handling. But most likely that is a switcher.

 

The power level you are talking about is so low either one would work fine.

[cglaeser 0]

Yes, that is 36W it has to get rid of if it is a linear reg. There is a possibility they are just rating the current capability though, not power handling. But most likely that is a switcher.

 

The power level you are talking about is so low either one would work fine.

 

Thanks. So, the linear has to dump the difference in voltage, but only has to match the current that is used, while the switcher is more efficient particularly at higher current because it switches on and off extremely fast, only using what it needs.

 

One other consideration. My electricity is relatively expensive at 0.35 cents per kwh. That really adds up. So if I were selecting a regulator for an 12VDC IR source, the wasted heat from a linear could cost more than the regulator in less than a year.

 

Best,

Christopher

[mike_va 0]

while the switcher is more efficient particularly at higher current because it switches on and off extremely fast, only using what it needs.

 

Sort of. The losses in a switcher are low not because of the speed per se, this allows smaller magnetics etc. The losses are low because when it has voltage across the power device it does not have current, and vice versa. The losses occur during switching, and some copper and core loss. Switcher can run from the low 10's of KHz up to 1MHz and maybe beyond. The duration of the switching action will be very small however.

 

I think it is easier for most people maybe to think of it as power in = power out (assuming no losses). For example, Pin=36V*0.1A=3.6W. Iout=Pout/Vout=3.6W/12V=0.3A.

 

For a linear reg you are constrained to Iin=Iout, but you are correct you have to dump that voltage (loosely speaking). In the case of a linear reg the voltage is present at the same time as the current, so you have higher losses that you are stuck with.

 

Hope this helps, I think I need a cup of coffee. We are wiring up another camera at home today...

 

P.S. yep that is expensive electricity. I measured my quad core that I run Vitamin D on last night, that was in the 1.7-2A range...

[ak357 0]

 

One other consideration. My electricity is relatively expensive at 0.35 cents per kwh. That really adds up. So if I were selecting a regulator for an 12VDC IR source, the wasted heat from a linear could cost more than the regulator in less than a year.

 

Best,

Christopher

 

Are we talking about "0.35 cents per kwh" or 35 cents per kwh ?

I would love to pay .35 cents per kwh

[cglaeser 0]

P.S. yep that is expensive electricity. I measured my quad core that I run Vitamin D on last night, that was in the 1.7-2A range...

 

Yeah, our electricity is tiered, and it goes even higher. Some of the homes in this area pay $1,200 per month. Large solar arrays are becoming more common. Holiday lights are significantly fewer this year.

 

I have a Watt's Up Pro and measure pretty much everything. I have replaced some items for free, just based on the savings.

 

Thanks again for your assistance. This thread has been very helpful.

 

Best,

Christopher

[bpzle 0]

I hate to high jack the thread, but since we're talking electricity bills... has anyone tried any of these devices that plug in past your meter and supposedly "lower" your bill by 15-30%? One of my buddies got one, was trying to explain it to my me but he's not exactly technically inclined...swears he's been saving on his bill though and it's perfectly legal. Although, he could just be trying to make himself sound less-stupid by validating his purchase.

[Soundy 1]

Yeah... grossly over-simplified, it's basically a big capacitor that sits across the legs of the circuit, where the phase shift "slows" the meter mechanism. It doesn't reduce your usage, it just makes the meter run slower and thus give lower readings.

 

AFAIK, they're not legal anywhere in the developed world.

 

EDIT: There's some discussion of it here, as well as a better description of how it actually works: http://uk.answers.yahoo.com/question/index?qid=20060627041826AAGt6oV

[bpzle 0]

My meter is digital anyway...

[cglaeser 0]

has anyone tried any of these devices that plug in past your meter and supposedly "lower" your bill by 15-30%?

 

I seem to recall many years ago in a physics lecture there was a discussion about inductive vs capacitive loads and that some companies would save money by adding a device that would balance the load. The imbalance is a function of the type of equipment used by the company. My (limited) understanding is that homes typically have much less of an imbalance, and the potential savings are therefore usually less.

 

Best,

Christopher