Probably a stupid question but I am adding a 30amp 12v power supply to my new control box for fans and LED power. Is there any reason I couldn’t leave the 3amp 12 volt jtech power supply out and run it directly to the same 30amp 12v supply?
Pretty sure the Jtech driver can only handle 2.5 amps of current. I suppose if you had a reliable way to make sure it was limited to that amount it is feasible. With the cost of the laser and driver I’m not sure I would personally chance it myself. There is a high likelyhood of blowing up your $350-$450 investment.
That’s what I was thinking but as stated above it would be an expensive “oops” so wanted to get some feedback on that plan before doing it to be safe.
The only issue that I can think of is not voltage or current related, but ripple. Some devices require a “clean” voltage. If you have too much ripple from the power supply they won’t work correctly.
However, I very seriously doubt that this would be an issue here.
This is going to all depend on how much current your “fans and LED power” are actualy drawing. You never stated an amount. You also never stated which “30amp 12v power supply” you’re using. Many companies over estimate. Rule of thumb is if it’s a cheap Chinese power supply then it’s probably not 30 amps. If it’s a name brand power supply (like a Mean Well) then you should be safe.
Ordinarily I wouldn’t think your fans would pull a large amount, but, fans are basically motors, and motors come in many different sizes, so if they add up closer to 20-25 amps then I would use the separate 3 amp supply just for the Jtech. If the motors are small then you should be safe.
Fans I have now are about 1 amp each so 6 amps. I am downgrading they are overkill so under 6 amps most likely. Lighting would likely only be a couple amps maybe another 6 amps max. I really only needed about 10 amps but cheap China power supplies were $15 for a 15 amp or $20 for the 30 so I figured might as well get the 30amp.
With the cheap Chinese power supplies you never know what you actually get, or how their circuitry is designed, but you should be OK. I would worry more about ripple as stated above by Larry.
1 Like
You only notice the headache when you stop drinking 
1 Like
In the event that there was ripples how would I know and what would it affect. More importantly could ripples damage the laser?
That all depends on the size of the ripples. Ripples are like voltage spikes, and a large enough one, especially on sensitive electrons like a laser, could effect it over time. I would add a UPS to the supply to help smooth out most issues. Of course if the power supply is really badly designed then it could create its own spikes, and then there is nothing that you can really do except learn from the damage it causes. Having said that keep in mind that most ripples are small and wear components down over time, but a few big ones and they start causing other issues. That’s why it never pays in the long run to buy cheap electronics for something as important as a CNC machine. I am using very high-end power supplies and I still will be adding a UPS to the system soon.
Depends on the design of the circuit. In a well made UPS (for example, APC) rectifiers convert AC power coming in to DC power. The DC power is then passed through the DC filters which consists of series inductance / parallel capacitance so ripple would be filtered out, BUT in a cheap UPS they generally end up with a saw toothed wave, which could cause it’s own issues. Many variables of course.
But the UPS is only connected to the A/C input of the DC power supply. I’ve never seen a hybrid AC to DC converter and UPS.
So that means that the DC Power supply will still generate it’s own ripple when it does its rectifying and AC/DC conversion.
The whole idea of A/C line filtering is garbage in, garbage out. You can’t expect a clean output even with the best power supply if you feed the device a bad signal. If you can clean your input, you can expect a better output HOWEVER, the device itself can still impart ripple on the output.
To answer the original question:
Try to find the power supply specs of the Jtech supply and see how they compare to your 30A supply. If its similar, then you can use it.
Maybe I am better off using the jtech piece to be safe. That being said another potentially stupid question. Is there any reason I can’t daisy chain the A.C. side and run both the 12v and 24v off one power cord?
The Jtech website doesn’t have any information that I can find concerning the power supply. It simply states that the kits come with a North American Power Adapter.
Can you post a picture of the label on the power supply which includes the voltage and current capabilities of the power supply?
I would use the adaptor that you got from Jtech. It has some features that your other power supply is not likely to have.
2 Likes
Using any just old power supply for a laser diode is potential for an expensive disappointment. I learned this the hard way after blowing out about $250 worth of diodes. 
3 Likes
Already decided to use the original to be safe. Thanks everybody
2 Likes
Not necessarily. As long as the power supply is regulated (which it almost certainly is) then there will be minimal ripple. If the design contains a ceramic output capacitor then the ripple will be reduced to almost nil. Add a LC output filter to that and even sensitive devices won’t detect the minuscule ripple it might have.
See above. The extra output stage will cancel out the ripple.
Safe is always good 
Certainly are a lot of ifs in that response.
1 Like