# Newbie Power Supply advice needed

#### Jamiel92

Joined Jan 26, 2020
5
Hi everyone,

This is my first post here. I am studying for a masters in engineering with the open university. I have only recently started so please forgive my novice vocabulary.

I am currently designing a personal project. The figures I am working with are as follows;
Voltage: 12vdc
Amps: 5.833
Power: 70watts

I have been scouring the net looking to find a power supply, input 240v (uk) to output 12v dc 5amp. There are a few plug in transformers to choose from but I would prefer to hard wire to my product. Can anyone help me out with what it is I should be looking for?

I basically just want something that I can run a plug and wire to my project and the voltage, amps and power is converted internally.

Last edited by a moderator:

Joined Feb 20, 2016
3,602

Joined Jan 15, 2015
5,646
Per the above I would look for a 12 VDC 10 Amp SMPS (Switch Mode Power Supply). If you want to hard wire this into your project I would look for an Open Frame version like this. Open frame allows for simple cooling in whatever your final enclosure is. The SMPS design allows for a wide input range usually 90 VAC to 240 VAC, 47 to63 Hz. They are compact and light weight. A 12 VDC 10 Amp linear supply will be large, bulky and have considerable weight. Anyway a minimum of 10 amps or greater rating.

Ron

#### Jamiel92

Joined Jan 26, 2020
5
These are all ideal but I'm looking for something a lot smaller. I considered after posting last night that I might make my unit battery powered which would avoid the need for bulky transformers.

My project is basically a fan heater, although I wont tell you the application

Joined Feb 20, 2016
3,602
A fan heater running on batteries may be a problem.
How long do you need it to run for?
You are talking about size limitations, I think a bettery will be larger than a power supply. It sounds like you need to work on about 6AH, so a "standard" SLA battery will run for just over an hour.
A 40AH car battery will give you around 7 hours.
If you go with batteries, you must incorporate battery over-discharge protection otherwise you stand the risk of killing the battery. Then you will need the correct charge controller.
A power supply sounds easier to me.

#### Jamiel92

Joined Jan 26, 2020
5
A fan heater running on batteries may be a problem.
How long do you need it to run for?
You are talking about size limitations, I think a bettery will be larger than a power supply. It sounds like you need to work on about 6AH, so a "standard" SLA battery will run for just over an hour.
A 40AH car battery will give you around 7 hours.
If you go with batteries, you must incorporate battery over-discharge protection otherwise you stand the risk of killing the battery. Then you will need the correct charge controller.
A power supply sounds easier to me.
I think as a minimum 3 hours of run time would suffice. As I may be taking this product to market, a bulky transformer wouldn't be the best option, nor the cheapest.

I can run it at 4amps as a minimum also which would respectively reduce the running temperature of the heater, of which I dont mind as i suppose it would allow the product to be safer.

Joined Feb 20, 2016
3,602
Here is an example Lithium battery I found with a quick search...
The 12AH battery is $81, 150x69x93mm. And a 24AH one is$160, 188x187x83mm.

How does that compare to a power supply in price and size?
Don't forget you will still need to buy a charger and battery management controller.

#### Jamiel92

Joined Jan 26, 2020
5
I agree a power supply would be better. I hadn't calculated the drain on a battery when I mentioned it. Are you aware of anything smaller that I can incorporate into my product or would it better for me to consider something which draws less power?

Joined Feb 20, 2016
3,602
It is hard to recommend anything as you have not revealed the application to any extent.
But, as you need a heater, the power supply is dependant on the heat requirement. Figure out what heat you need then work back from that.
Allow a bit extra from the powersupply for losses.
You may just have to wear the size limits. But do use a bigger rated powersupply than you need, otherwise the life of the supply will be greatly reduced if you run full capacity all the time.

Joined Jan 15, 2015
5,646
These are all ideal but I'm looking for something a lot smaller. I considered after posting last night that I might make my unit battery powered which would avoid the need for bulky transformers.

My project is basically a fan heater, although I wont tell you the application
Well design is all about trade offs. It takes considerable electricity (power) to make heat so you may want to keep that in mind when considering a battery. On the bright side battery technology has improved considerably in recent years. Once you decide your power requirements you can move to a source of power.

Ron

#### Dodgydave

Joined Jun 22, 2012
9,479
Hi everyone,

This is my first post here. I am studying for a masters in engineering with the open university. I have only recently started so please forgive my novice vocabulary.

I am currently designing a personal project. The figures I am working with are as follows;
Voltage: 12vdc
Amps: 5.833
Power: 70watts

I have been scouring the net looking to find a power supply, input 240v (uk) to output 12v dc 5amp. There are a few plug in transformers to choose from but I would prefer to hard wire to my product. Can anyone help me out with what it is I should be looking for?

I basically just want something that I can run a plug and wire to my project and the voltage, amps and power is converted internally.