ebay power supply

[HankMcSpank]

I,ll second this my, 3 ps arrived today and i,m well chuffed they just look and feel quality.
Thanks Irving and Kip.:clap:

Edit: ended up costing me £17.38 each inc delivery that was for 6 supplies.

I,ve just been quoted £16.00 Del for 3 of these to yorkshire from the seller and they are on there way as we speak.

Could you clarify (so I can put on my best haggling hat ) - excluding delivery...what did he charge per PSU?

[HankMcSpank]

Thanks (& sorry for labouring the point! )

For anyone wanting to order a few of these - the seller will allow collection via your own courier.....& Parcel2Go will deliver upto 25kg to your door for about £7.50 in total (the ad says they weigh 2.5KG each, so factoring in some 'headroom', you could therefore get 9 PSUs into the one Parcel2Go delivery - can't imagine you'll be popular with the driver though!)

[John S]

So after the sage of parcel farce, parcels 2 go etc was it possible to get to around the 40 volt mark ?

.

[Swarfing]

Hank

i bought two of these a while a go before seeing this original thread and still not got round to powering them up let alone start to tweak them. i would be very interested in anything further found out about them on the voltage drop front. My drivers can do the full 50v volts but would be happier at a few volts lower to save the possible crispy bacon burn factor. By the way i picked mine up direct from the old fellow (i live in Swindon)

[ecat]

Adding up the costs of a diy cnc machine continues to make my eyes water so finding these makes for a refreshing change :)

In theory the output from the opto isolator should be wired to a feedback pin on the main PWM controller chip. If memory serves me correctly and the chip follows convention then the function of this feedback pin is very simple:

if the voltage on this pin is above a certain threshold value (around 2.5v perhaps) the PWM controller switches off and if the voltage on this pin is below said threshold the PWM controller switches on - this is how the output voltage is regulated.

As the PSU already has some way of varying the output voltage there may be some additional complications but all that should be needed to decrease the output voltage is a change to a single resistor such that the voltage on the feedback pin is increased by about 20% for a 40v to 47v output range (ish).

Disclaimer: I know enough to hurt myself and nothing more :)

[HankMcSpank]

I'd have thought the way they do this is to modify the duty cycle of a PWM stream. I'm tempted to order one - it appeals to the lazy mountaineer side of me ("I want to climb it because it's there" or transposed to this particular situation "I can't be arsed to climb a mountain, so I want to get the voltage down on this 50V PSU because erhm it's not 45V")

[Tom]

I bought one ages ago (as a result of this thread) and just plugged it in. It's been running the machine ever since.

Open circuit my supply measures 42.7V (the data sheet spec is 42.8V +/- 0.5V, so no worries).
The data sheet calls this voltage "out of regulation" (ie. there's less than 5.5V or more than 13.5V on Ucr). I haven't checked what happens when I put voltage on Ucr, because the "out of regulation" voltage is the one I want, and it seems to cope with load OK at 42.7V. The 4.3 signal diagram on the datasheet (attached) is the useful one.


On my machine Ucr (pin 28) is just floating, but I should probably tie it to ground to avoid surprises. I haven't bothered because, well, it just works.

Happy days.

[HankMcSpank]

Thanks for the feedback - have you measured how much the 'out of regulation' 42.7V moves when your stepper motors are going at full tilt?

[Tom]

It doesn't flinch at maximum speed. I can't measure it under cutting load at the moment because there's some dust-sensitive stuff in the room, but jogging at max speed I can't even measure 0.1V variation on the output pins of the supply. Steppers under load should only consume marginally more power i'd have thought.

I'm running with the 3Nm steppers that everyone sells, along with the 4.2A drivers.

One test I can't do is a hardware e-stop, to see what voltage gets pushed back through the drivers with a sudden stop. I'm still only wired into software e-stop circuit (not good), so I can only decelerate at the max values EMC2 allows. Still, with 7V of headroom to the 50V max which the drivers can cope with, hopefully no problems...

[John S]

Tom,
You say 42.7 volts but the spec says 50v ?
Is this with it turned down as far as it will go ?