Quick power supply question

Electronics
#1

So I’ve been looking to find a small 110v to 24v converter and I keep finding either really big or really small ones and I don’t know what makes the difference in terms of size. My guess os because of the amp rating (look at examples) so the question is, what is the most compact way to convert from 110v to 24v 4amp? I intend to create a board for a product and I’m not sure what a realistic footprint would look like for this particular part of the board. Is the amp rating the only reason?

Examples
For the first one you select 110 to 24v and the one in the picture appears.

Thank you for your help.

#2

Current capacity is usually the main factor in size. Efficiency is another factor. Less efficient means more heat to dissipate which requires surface area. Keeping everything reasonably cool will promote the reliability and life of your product.

What is the max current draw of your brd/project? Determine that and add some headroom.

Is using a wall wart a possibility?

#3

Also, when designing your pcb, you need to take into account the current the traces will be carrying. 4amps is substantial current, and the trace width needs to take that into account.

http://circuitcalculator.com/wordpress/2006/01/31/pcb-trace-width-calculator/

1 Like
#4

Hi artg

Thank you for clarifying that. The current requirement is 4 amp max. Is this too much for a wall wart? We talked about the possibility of a WW but ideally we would keep all contained in a small board. If this is not possible we’ll end up with the WW.

#5

At 4A you’re looking at 96W. Depending on the duty cycle of the 4A, that pwr sply rated at 6A may be the way to go. Get one and load test it to see how warm it gets. 6 Ohm, 100W resistor. Mount on standoffs to allow air flow around it. Design your enclosure accordingly.

@wandrson makes a very good point about pcb traces handling 4A. Over spec just like the pwr sply.
PCB tip - if heavy current carrying etch has to go from one side to the other, use a plated through vias with a component lead in it.

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#6

A cheap quick and dirty way to make a dummy load to test a 24 volt power supply is available at your local auto parts store. Buy two headlight bulbs and put them in series. This will be a lot cheaper than a 100W resistor. If needed you can mod it with a power NPN transistor, a pot and two resistors to make it a variable resistance dummy load.

As to the power supply itself, it will typically be cheaper to buy a wall wart supply unless you are doing a fairly high volume.
That said, if you are determined, to have the power supply integrated in side your unit with a small footprint then you will likely want a switching power supply, as they typically offer the best results in size and weight. The downside is that it is often necessary to add extra filtering and shielding to prevent the power supply from interfering with the operation of the gadget it is powering. Dealing with these issues can be as much trouble as the power supply design and build.
If you are interested in these things, I have already made a post to see if there is any interest in teaching the basics of power supplies eg building an unregulated supply, making a voltage reference, linear and switching regulators.