4axis HCNCPRO and Power supply

[toneV8]

FINALLY I order 4 axis HCNCPRO and wait to arrive. When arrived then I start soldering pcb and building power supply, after electronics will start building cnc milling machine of course I with post pictures.

[toneV8]

Today arrive 4 axis HCNCPRO I am so happy. Next step building power supply.

[toneV8]

I buy this transformer.
input: 220V 8,5A
output: 22V 34V 38V 44V 52V 56V 34,5A

bridge rectifer: I have two International rectifer 36MB80A see attached PDF file 35A 1200V

capacitors:
I have two 40.000 mFD 40VDC 50VDC max
I have two 100.000 mFD 15VDC 20VDC max
I have one 12.000 mFD 75VDC 95VDC mac
I have one 68.000 mFD 25VDC
I have one 10.000 mFD 25VDC


I plne to use this with HobbyCNC PRO 4axis

Can someone help me to select proper voltage and capacitors for power supply.

If I use output 22V and multiply with 1,4 I will get 30,8V
If I use output 34V and multiply with 1,4 I will get 47,6V this is more then 42V max voltage allows HobbyCNC PRO 4axis

Does it possible to reduce voltage from 47,6V to 40V.

What kaind fuse to use

What kaind wire 1,5mm square or 2,5mm square to use for transformer -> bridge rectifer -> capacitors -> HobbyCNC PRO 4axis

[toneV8]

312 views but nobody to reply.

[sergio007]

Nop, no way to effectively lower the tension without big loosing !

Best is to use the 22 Volts AC, after rectifing and filtering (Capacitor) you will get near 33 Volts or little lower.

If you look Hobbycnc, they suggest 35 maximun to be safe but yes the top limite is 42 volts but don't reach it is my suggestion.

Alp
Sergio

[stefants]

I really don't know what I'm talking about here, but after reading lots and lots of stuff over the last few days, I think that maybe pminmo's description of a DC power supply offers a possibility for dropping the voltage down from the ~47VDC you're anticipating if you use your 34VAC tap. I think the series diodes are effectively operating as resistors in this case, meaning you're just turning the extra voltage into heat loss, but if you really want the 40VDC, this might be a way to get it.

http://pminmo.com/simpleps.htm

[toneV8]

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[toneV8]

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[Al_The_Man]

First you need to ensure this is not an auto-transformer, IOW the secondary should be totally isolated from the primary.
What you have used there is thermal circuit breakers, which should work OK, they are not fast devices as there is a time delay before tripping.
The bleed resistor could be around 2.5k 2watts across the caps.
If you are absolutly sure it is an isolated transformer, you can ground the DC common if you wish, if so, do not ground the AC secondary!
Set up a ground plate and take all grounds to one point.
To modify the transformer, you could remove turns if you wish, to reduce the voltage, it is harder to do on a square lamination than a Toroidal, however.
Also you could use the 20v lead out as one leg and wind more on connected to the 56v terminal until you have 40v with respect to the 20v.
Al.

[stefants]

>1. where I need to earth grounding
-If there's not an obvious ground terminal on your transformer, I'd connect the ground to the base of the transformer. Use a multimeter to check that there's not a short between the base of the transformer and any of the power connection terminals first (while the transformer is NOT connected to power). If you find a terminal that's shorted to the base, that's the ground...hook up your ground wire to that terminal. If no terminals are shorted to the base of the transformer, hook the ground lead to the transformer base itself.

>2. In input can I use 10A magnetic fuse like on pic ( I dont know does it >corect term for this )
-You can put that circuit breaker ("magnetic fuse") inline on the supply side (220VAC) side of the transformer, but it won't do anything unless there's a wiring fault or a short somewhere in the supply side of the circuit. It's not a bad idea to have it there, but your steppers will NEVER draw enough current to make that breaker pop. 24VAC at 10A on the stepper side of the transformer shouldn't draw anything more than about an amp on the 220V supply side.

>3. On capacitor do I need to put resistor and what kaind
-Check the site I linked to above...the resistor used there to bleed down a 40F, 40V capacitor operating in a 32V system was 470 ohms, 2W. I would definitely put the bleeder resistor in place across the terminals of each capacitor you have in the system so that after you shut off the power, the charge stored in the capacitors dissipates. That'll take some time...it's not instant. Be careful when handling them. They can provide one heck of a shock when charged.

>4. what kaind LED I need to put on AC and DC circuit
-You don't need LEDs at all. They're a nice feature to include so that you can see that the power supply is on and functioning, but you don't need them. Personally I'd skip them. The biggest advantage of having one would be to identify when the capacitors had discharged sufficiently to handle the capacitor(s) again. I think all you'd need is to hook up a resistor and LED in series and attach that combination in parallel to the DC output line. The resistor would have to be chosen to limit the current going through the LED appropriately for the 32V drive.

>5. In input can I use 10A fuse like on pic
-The OUTPUT fuse/circuit breaker (the one on the DC side of the rectifier) looks fine. What's the current draw of the motors you've got? It's possible you could use a smaller breaker and be a little safer, but it depends on the rating of your motors. It wouldn't be a bad idea to fuse the individual motor drive lines separately instead of using one 10A fuse to cover all three. Something like a 3A breaker on each motor might be a better choice (depending on the motor ratings). But the 10A for all three is probably fine the way you have it in the picture you provided.

>6. maybe something else that I miss to notice on power supply
-I'm not sure you need two capacitors inline. The power supply reference I gave above just used the one capacitor. Having two won't hurt, but you probably don't need them both.

[Al_The_Man]

Originally Posted by stefants > -You can put that circuit breaker ("magnetic fuse") inline on the supply side (220VAC) side of the transformer, but it won't do anything unless there's a wiring fault or a short somewhere in the supply side of the circuit. >

This breaker will also react to excess load on the secondary or DC etc, any current 'down stream' of this breaker will be reflected back through to the primary.
In fact I rarely fuse the secondary side, If I do it would be on the AC input to the Bridge, Also if the the fuse or breaker opens where you have it after the cap., any reverse high potential caused by switching off the inductive loads has nowhere to go to or be able to be discharged safely without the drives carrying the full brunt..
Al.

[NGinuity]

Originally Posted by stefants The resistor would have to be chosen to limit the current going through the LED appropriately for the 32V drive.

For a 32 volt drive, the resistor would have to be at least a 1 watt variety for the amount of current it is dissipating. I recommend a 2 watt resistor to keep your LED and resistor working for a long time.

So, you will need a 2 watt 1 Kilo-ohm resistor in front of your LED. This is how I got that figure:

A Standard LED runs in the neighborhood of 3.4 volts forward, dissipating 30 mA power. This is an average, safe figure.

To get our resistor figure, we use the equation
resistance = ( supply voltage - LED voltage drop ) / amperage
(32 v - 3.4 v) / .03 amps = 953 ohms and change.

If we round it up to the next available value, you need a 1 Kohm resistor.

For the wattage figure....

wattage = (supply voltage - LED voltage drop) * amperage.

(32v - 3.4v) * .03 amps = .858 watts <--- This is just our constant wattage. To get our safe wattage rating, we need a resistor at least 1 and 2/3 the rating above:

.858 watts * 1.66 =~ 1.424 watts

The next value up is 2 watts, since 1.424 sits in between 1 and 2.

For your fuse....

I would recommend a slo-blo if you have problems with correctly rated fuses blowing on startup.

It looks like you have a good start so far though. How were you planning to turn your power supply on? I assume you were going to put a rocker switch on the DC side? If that is the case, you could save a little money by using a transistorized drive for the power switch.