How much current can a tin solder track handle?

Thread Starter

Fired21

Joined Jul 16, 2019
4
I'm working on a DIY project where I need to control some 9V solenoid valves with an arduino. I don't have the tools to make a PCB myself, so i choosed to work on perfboards.

Now, I have to connect power supply (MeanWell ) to the step down regulator (Polou D36V50F9) that powers the solenoid valves, and I'm doing it with a solder track. My power supply is capable of sourcing 4,5 Amps at 12V, with a total power of 54W.

Can a solder track hadle all that power? How wide should it be? How thick?

Note: My solenoid valves are latching, and this means that they need only a short pulse to open and close (opposite polarity), and i can control them one at a time to minimize the current. But i want to be sure that my circuit won't burn in case the program does not work properly.
 

Alec_t

Joined Sep 17, 2013
11,526
Welcome to AAC!
Different quality perfboards are likely to have different copper track thicknesses and hence different current-carrying capability. If in doubt, solder a tinned copper wire along the track to reinforce it.
 

Irving

Joined Jan 30, 2016
948
Its not what your supply can deliver that matters, its what is required by the end-point. I couldn't, on a quick search, find the coil resistance of the 9v solenoids. But lets assume you have 45 ohm coils, using ohm's law that's 9/45 = 200mA each, and, say, 10 solenoids = 2A.

The track width calculator says that the width needed for 2A over 100mm of standard 1oz copper is 0.78mm. Perfboard traces are just under 2mm but are pierced. If the holes are filled that should be OK, if not add some solder or parallel up 2 or more tracks.

edit: Vero don't publish official figures but various pundits over the years say 0.5 - 1A allowing for a 10degC temperature rise...
 
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Thread Starter

Fired21

Joined Jul 16, 2019
4
Its not what your supply can deliver that matters, its what is required by the end-point. I couldn't, on a quick search, find the coil resistance of the 9v solenoids. But lets assume you have 45 ohm coils, using ohm's law that's 9/45 = 200mA each, and, say, 10 solenoids = 2A.

The track width calculator says that the width needed for 2A over 100mm of standard 1oz copper is 0.78mm. Perfboard traces are just under 2mm but are pierced. If the holes are filled that should be OK, if not add some solder or parallel up 2 or more tracks.

edit: Vero don't publish official figures but various pundits over the years say 0.5 - 1A allowing for a 10degC temperature rise...
I'm not using that type of perfboard ( called stripboard i think). I'm doing the tracks myself only with the solder tin, connecting adjacent pads. I know it sounds weird, but it works!
Now are solder tin traces and copper traces the same?
 

jpanhalt

Joined Jan 18, 2008
10,095
Solder has a higher resistance than copper. Copper and solder are not the same. Current rating is actually a temperature rating -- often a 10°C rise in temperature is used as an acceptable limit, but a higher temperature rise may be acceptable. If you need more current, you can solder copper wire on top.

"Perf" board can be virtually anything with with holes in it on which you can construct a circuit. Some perfboard has no copper to begin with. We used to insert pins and connect them with wire. At the other extreme it can have copper laminated on both surfaces or even plated through holes. If you need more current carrying capacity, just add thicker wires or more solder.
 

Thread Starter

Fired21

Joined Jul 16, 2019
4
T
Solder has a higher resistance than copper. Copper and solder are not the same. Current rating is actually a temperature rating -- often a 10°C rise in temperature is used as an acceptable limit, but a higher temperature rise may be acceptable. If you need more current, you can solder copper wire on top.

"Perf" board can be virtually anything with with holes in it on which you can construct a circuit. Some perfboard has no copper to begin with. We used to insert pins and connect them with wire. At the other extreme it can have copper laminated on both surfaces or even plated through holes. If you need more current carrying capacity, just add thicker wires or more solder.
Thank you for your detailed explaination! I didn’t think about soldering a wire on top of the track, nice advice. Btw, the perfboard I’m using is that type called prototype board, with a number of pads not connected between them. Search it on google images to see them.
 

jpanhalt

Joined Jan 18, 2008
10,095
This is one type I use.
1595505363954.png
Note the holes are plated through. Moreover, 1206-size SMD's solder nicely between holes and one can run connections on the either side. 24 AWG wire works well. I like Kynar insulated wire over PVC, as the insulation doesn't melt back or burn, and it is big enough to be easily stripped mechanically.

Wire-wrap wire is similar but usually a smaller gauge. You can also use a soldering iron tip to split that insulation, but I don't like to abuse my iron like that.
 

MrChips

Joined Oct 2, 2009
21,666
Take ordinary solid 22AWG or 24AWG hookup wire. Strip off the insulation and lay it along the board as you wish. Tack solder the bare wire to the pads below.

If you need to have any wires crossing over just keep the insulation on the wire crossing over.
 

Irving

Joined Jan 30, 2016
948
I use prototyping board as well with just the pads and join with various wire types. I use 'magnet' wire to join components because you can solder through the insulating layer; so much less hassle. For higher current I agree with jpanhalt, kynar or silicone insulated single strand from 24 through 18awg. Don't use multi-strand, its too easy to end up with random shorts due to little fragments.

I use this approach sometimes to mimic pcb layout to get a feel for routing compleity and evaluate noise, crosstalk, etc.
 

Thread Starter

Fired21

Joined Jul 16, 2019
4
Thank you guys for all your replies! Is this cable good for what you're saying? It's AWG 24. Unfortunately this is multi-strand, but i currently have only this type of cable
Cavi.jpg
 
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jpanhalt

Joined Jan 18, 2008
10,095
Can't tell from the pictures:

1) While plain copper can be soldered, if it is plated with tin or silver, it is much easier to solder. Is the wire itself copper color or silvery?

2) Many people don't pay much attention to the insulation. I do. Kynar is more expensive, but once you use it for bread boarding, you won't want to change. Any insulation will work. Some people even use wire without insulation, but then you have to be more careful to avoid shorts.
 

Irving

Joined Jan 30, 2016
948
Another option is bare, tinned, solid copper wire, with sleeving added where insulation is required.
Yes, I've done it that way too, but its such a faff. Magnet wire, or solder-through wire-wrap wire which is similar, is by far and away the quickest and easiest. Solder one end, route if need be, or point-to-point, solder other end, wiggle to break off, repeat... no messing around putting stuff down to pick up cutters, wire strippers.

Only caveats are:
don't use above 50v except with caution.
use fume extraction (you should be anyway).
use a good high-temperature solder, at the right temperature
use the right tip on the iron - i favour a narrow chisel bit, thin conical doesn't have enough thermal mass
 
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