Is 22-Guage Stranded Hookup Wire the correct wire to connect the Switching Powersupply to RAMPs 1.4?

1

I obtained the following wire 22 Gauge Stranded Hookup Wire from Radio Shack:

Type/Style: AWM/1007
Wire Gauge: 22 AWG
Insulation Thickness: AVE. 0.42 mm
Rated Voltage: 300V
Temperature Rating: 80°C / 176°F    

Use Limitation: Internal wiring of appliances; or where exposed to oil at a temperature not exceeding 60°C or 80°C, whichever is applicable.. Tags may indicate the following: 600V Peak - For Electronic Use Only.

I'd like to be able to hook up RAMPs 1.4 to my switching power supply with this wire. Will this work okay?

leeand00

Posted 2016-03-25T15:24:37.770

Reputation: 1 853

Answers

1

22awg wiring is good for a max of 7A in this usage case. Your power supply can provide 30A. So it is definitely not large enough wire gauge for good wiring practice -- in the event of a short, you want the PSU's over-current protection to kick in before the wiring overheats. That would mean 14ga between the PSU and board. 16ga would probably cover your actual load requirements just fine, but we need to know a lot more about your printer to say that for sure.

12v systems need heavy duty wiring, at least on the main supply lines. You can use 22ga for individual power consumers, such as fans, extruder heaters, etc. (No heatbeds.)

Ryan Carlyle

Posted 2016-03-25T15:24:37.770

Reputation: 6 346

I think you mean "in the event of an overload". In the event of a dead short the protection should kick in almost immediately, well before the wires have any chance of heating up. – Tom van der Zanden – 2016-03-25T18:30:29.120

It's not uncommon for PSUs to allow significantly higher draw than their rating before the overcurrent protection kicks in. For a high-current, low-voltage PSU like this, the supply wires, terminals, board traces, etc can provide enough short circuit resistance (a few tenths of ohms) that a dead short won't actually trip the overcurrent protection fast enough to avoid immolating undersized components. – Ryan Carlyle – 2016-03-25T19:52:48.777

Yet another reason why we should all be switching to 24v PSUs... way safer than 12v PSUs. Less risk of wire heating, smaller wires for less wire fatigue on moving parts, and much more reliable tripping of over-current protection. – Ryan Carlyle – 2016-03-25T20:08:19.443

@RyanCarlyle When you say 22ga above do you mean 22awg ? Is ga shorthand for awg? – leeand00 – 2016-04-10T06:54:35.683

@RyanCarlyle I ended up using AWG 10 wire type MTW OR THWN OR THHN (it's a pretty thick wire) for the wires between the switching power supply and RAMPS 1.4. It's good up to 600V, it's overkill but I think it'll do the trick. – leeand00 – 2016-04-30T12:02:07.323

0

That should be fine for powering RAMPS, steppers and extruders but it is on the thin side. To err on the side of caution you should use somewhat ticker wires. However, you should definitely use thicker wires for the heated bed connection.

Tom van der Zanden

Posted 2016-03-25T15:24:37.770

Reputation: 14 003

Definitely not big enough gauge for a heated bed. Actually, it's probably not big enough for steppers and a 12v extruder either. – Ryan Carlyle – 2016-03-25T18:15:02.977

@RyanCarlyle That seems to contradict your own statement that it's good for 7A. 7A is more than enough enough to power an extruder and steppers though if you have very beefy steppers and drivers to match you might run into trouble.

– Tom van der Zanden – 2016-03-25T18:26:24.140

A 40w 12v extruder draws 3.3A alone, that's half your "absolute max" wire capacity. Then each stepper is likely to be between 0.3A and 2A, depending on stepper specs, driver selection, current setting, etc. (PSU load is max 1.41x higher than the current setting at half step positions with both coils energized.) Call it 1A each, w/ four steppers = 4A. Now you're over the wire rating, before considering the controller board and fans. You MIGHT be ok if you preheat with motors de-energized, and have good motor selection so the chopping drivers run efficiently and reduce motor draw from the PSU. – Ryan Carlyle – 2016-03-25T20:00:33.563

And don't forget, 7A is "chassis wiring" rating, which means the wire is allowed to heat up considerably. Conservative rating should be a fair bit less than that. – Ryan Carlyle – 2016-03-25T20:02:02.960

The 40W extruder example is a bit contrived, since PWM will keep the average power draw much lower than the maximum (and during heat up, steppers would generally not be enabled). The video shows that 3A can be enough to run a printer just fine. I agree 22AWG is on the thin side, and edited my answer to reflect that. If you want to get completely technically within the specs, you have to account for the fact that the connectors on RAMPS aren't even rated for 30A so no matter how thick you make the wires, you'll always have that point of failure before the PSU enters protection mode. – Tom van der Zanden – 2016-03-25T20:16:52.870

Not contrived at all -- many/most people home while preheating, and there's the mid-print cold-pause and resume case too. Max heater power for >1min with steppers engaged is an expected load case. In a NORMAL operations, yes, PWM drops the average current draw for both steppers and heaters. But we don't know what kind of crappy off-spec parts are being used here. Maybe they're 12v rated motors that will run the drivers at 100% duty cycle instead of proper low-inductance motors that will only need ~30% duty cycle. That alone is likely to max out 22awg wiring. – Ryan Carlyle – 2016-03-25T21:51:09.887

And good point on the connectors. We need to be very careful to only give very conservative advice when it comes to newbies playing with electronics that can burn their house down. That means factoring in worst-case load combos and all the weak links everywhere in the circuit. – Ryan Carlyle – 2016-03-25T21:53:08.340