General questions of best power design for 110v 12v 5v 3.3v etc.

Thread Starter

gopalnn

Joined May 22, 2024
3
Hello wonderful people. I have a general design question. I have a device (load) (reptile chamber) which requires 12v at 4 amps and 5 v at 1 amp. There r several ways to get power into this device so I was looking for best practices for what to follow. I have 3 choices:

1. 110v wall wart to 12v dc as input into machine and buck converter the 12v dc down to 5v and 3.3 for microprocessor power and control. (There are also 12v devices like fans that run in the system). But wall warts peak at 5a or aroundb60 watts.
2. 110v desktop power supply into 12v (the kind with a thick brick that plugs into 100 and outputs 12v dc. Then similar down convert for 5v and 3.3v.
3. 110v wire straight into device and use unframed power supply in device for power conversion 110v to 12v and down....
4. One of the "parts" of the device is a heater. The heater is 50 watt heater. So 4.x amps or so. This "heater part" can be powered with 12vdc at 4 amps or 110v at .5 amps ( same wattage) . All other "parts" are 12v 5v or 3.3v so this could work too.

My general questions:
The device is a reptile chamber to provide humidity and heat for the critters inside.
1. Is 110v straight into device with unframed power supply going to be an issue?
2. Is it better to use 110v ac or 12vdc to power the heater? The heaters come in all sizes and wattage so I can use appropriate heaters based on input voltage.
3. Will there be any issues into the future with for example trying to get the product UL listed?
4. At 12vdc 4amps the leads to the heater do warm up considerably. I have used 18 awg wire for power leads but ground wire is still quite hot. Should I upgrade the wiring to 14awg? Or more? I looked up that 5amps is ok with 18awg wire.
5. Cost scenarios - anyone have any ideas as to cost of one solution vs. Another? If it is all comparable I would go for best design. But if say going 110v av to heater element costs twice as much due to supporting hardware, connectors, etc. then I know which way to go (assuming I won't burn the house down with a melted lead. )

Any help would be appreciated. Thanks one and all for your input.

I can provide additional details of the setup if required. I wanted to keep it rather generic vs. Discussion of my exact product. Thanks again.
 

ronsimpson

Joined Oct 7, 2019
3,220
I hate to run 110Vac around the house and into an animal cage. That is why I like a wall-wort power supply. Get the voltage down before you run the wires.
 

dl324

Joined Mar 30, 2015
17,142
Welcome to AAC!
1. Is 110v straight into device with unframed power supply going to be an issue?
110VAC in an unframed power supply will leave lethal voltages exposed.
2. Is it better to use 110v ac or 12vdc to power the heater? The heaters come in all sizes and wattage so I can use appropriate heaters based on input voltage.
What voltage does the heater use?
3. Will there be any issues into the future with for example trying to get the product UL listed?
Cost will be the primary issue. In addition to paying to have it tested, you need to pay for continued approval.
4. At 12vdc 4amps the leads to the heater do warm up considerably. I have used 18 awg wire for power leads but ground wire is still quite hot. Should I upgrade the wiring to 14awg? Or more? I looked up that 5amps is ok with 18awg wire.
18AWG is rated for more than 10A. How long are the wires?
5. Cost scenarios - anyone have any ideas as to cost of one solution vs. Another? If it is all comparable I would go for best design. But if say going 110v av to heater element costs twice as much due to supporting hardware, connectors, etc. then I know which way to go (assuming I won't burn the house down with a melted lead. )
Use switching regulators to generate the voltages lower than 12V (use a switching regulator for 12V too).
 

Thread Starter

gopalnn

Joined May 22, 2024
3
Thanks @ronsimpson. Wall-warts peak at 5A, so, I guess the next best is the "brick style" as ugly and irritating as they are.
Thanks @Dennis. The heater is currently a 12v 50watt heater. I have VERY short leads 5 cm 18AWG to the heater. I will recheck my wiring (and load). Will use switching regulators for step-down.

It looks like the 110v straight-in is not worth the "hassle" (safety wise or cost-wise).

Last question - Can 12v DC 4AMPS uncontrolled (I.E. loose wiring for example) cause any serious safety issues (for either the critters and humans)? What could a loose 12V DC 4Amp source do? Can it catch fire? I am assuming there could be arcing/sparks?
 

Reloadron

Joined Jan 15, 2015
7,580
At 12vdc 4amps the leads to the heater do warm up considerably. I have used 18 awg wire for power leads but ground wire is still quite hot. Should I upgrade the wiring to 14awg? Or more? I looked up that 5amps is ok with 18awg wire.
Would this be a ground wire or neutral wire? Can you provide even a rough drawing?

Personally I would run with 12 VDC using a 12 VDC power supply. A 12 VDC 10 Amp supply is inexpensive. Since your 5.0 volt current demand is low I would just use a buck converter off the 12 volt supply. I would wire my heaters with AWG16 and no leads should get hot. This is merely how I would go about it.

Ron
 

Thread Starter

gopalnn

Joined May 22, 2024
3
@Reloadron - Thanks for the info. As for the wire issue, I think I have it figured out. What I thought was 18AWG was in fact mislabeled 24 gauge wire. Bad me for not checking my wiring. Yes, I think I will go with high-power 12v "brick" with enough reserve for anything else. 10A should be more than plenty for everything I need.
 

Reloadron

Joined Jan 15, 2015
7,580
@Reloadron - Thanks for the info. As for the wire issue, I think I have it figured out. What I thought was 18AWG was in fact mislabeled 24 gauge wire. Bad me for not checking my wiring. Yes, I think I will go with high-power 12v "brick" with enough reserve for anything else. 10A should be more than plenty for everything I need.
You can find a buck converter like these which are inexpensive and will give you 5.0 volts or 3.3 volts, pretty much whatever you want at a few amps no problem foe your low voltage low current needs.

Have a good one...
Ron.
 
Top