Power Supply Suggestions please..

[Jonathan]

Yes that's better, still seems OTT though. 4x25v would have been slightly better, but it's not a big deal.

With that transformer you will be able to get multiples of 35V, so 70V for the motors and 35V for other things. What voltage do the other things require?

[Ricardoco]

Yes that's better, still seems OTT though. 4x25v would have been slightly better, but it's not a big deal.

With that transformer you will be able to get multiples of 35V, so 70V for the motors and 35V for other things. What voltage do the other things require?

The other things range from 12v to 32v but the contactors can be what ever i want when i order them.

[Jonathan]

The other things range from 12v to 32v but the contactors can be what ever i want when i order them.

Presumably the contactors are just to switch these other things on and off?
The absolute minimum you can get from the transformer you have bought is by using one 24v winding, which when rectified will give 24*2^0.5-1.1=32.8V which is clearly above 32V so probably not much use. Also the tolerance on the mains voltage (230V +10% - 6%) means that it could be up to 32.8*1.1=36.1V.

How much power do these other things need? Can you provide a list of voltage and current or power that each device uses so we can work out the best transformer? It sounds like you'd be much better off with a separate transformer, perhaps 16V.

[Ricardoco]

Presumably the contactors are just to switch these other things on and off?
The absolute minimum you can get from the transformer you have bought is by using one 24v winding, which when rectified will give 24*2^0.5-1.1=32.8V which is clearly above 32V so probably not much use. Also the tolerance on the mains voltage (230V +10% - 6%) means that it could be up to 32.8*1.1=36.1V.

How much power do these other things need? Can you provide a list of voltage and current or power that each device uses so we can work out the best transformer? It sounds like you'd be much better off with a separate transformer, perhaps 16V.

If i was comming out and used non regulated that would be a problem but i will build a circuit to give me all the voltages i will ever need. Besides which they are on their way to me this moment.

rick

[Jonathan]

If i was comming out and used non regulated that would be a problem but i will build a circuit to give me all the voltages i will ever need. Besides

The problem is unless it's less than a couple of amps it's hard to regulate the voltage, since linear regulators are extremely inefficient so you can only use them for quite small currents, SMPS's are quite difficult to design and adding more transformers is rather illogical, so I'll be interested to see how you plan to change the voltage. Also if the other appliances only use a small amount of current (making it reasonable to use linear regulators), then the transformers are probably several times bigger than they need to be.

[Ricardoco]

The problem is unless it's less than a couple of amps it's hard to regulate the voltage, since linear regulators are extremely inefficient so you can only use them for quite small currents, SMPS's are quite difficult to design and adding more transformers is rather illogical, so I'll be interested to see how you plan to change the voltage. Also if the other appliances only use a small amount of current (making it reasonable to use linear regulators), then the transformers are probably several times bigger than they need to be.

So you really think that they will be too much for 5 steppers and a few low amp (Less than 5A) power supplies providing 12V 18V 24V and maybe even 36v. I will be using circuits based on LM317's (or equiv) driving 2n3055s...

Rick

[Ricardoco]

Jonathan, Check your mail..

[Jonathan]

So you really think that they will be too much for 5 steppers

There's nothing wrong with having too much power available - it's just generally doesn't make economic sense.

and a few low amp (Less than 5A) power supplies providing 12V 18V 24V and maybe even 36v. I will be using circuits based on LM317's (or equiv) driving 2n3055s...

Earlier you said you didn't want to make a power supply when it was just a transformer, rectifier and capacitor, but now you're suggesting a lot more components to get what you could have made for less money by just using the correct voltage transformers. For the 12V and 24V you could have used a transformer with two 9V secondaries, which would be much cheaper, easier and more compact. 36V can be had from the stepper motor transformer. 18V from a 12V transformer.

A linear PSU made with LM317's and 2n3055 transistors may work, but the power it dissipates will be huge. Say you're using 12V at 5A - the voltage across the transistor Collector-Emitter junction is 32.8-12=20.8V. At 5 amps that means your transistor has to dissipate 20.8*5=104W. The absolute maximum rating for that transistor is 115W (TIP3055 only 90W), but that's not enough since as the transistor junction to case thermal resistance is thermal resistance is 1.5°C/W, even with a perfect heatsink it can only dissipate (150-25)/1.5=83W at 25°C ambient. Add to that another few of these circuits and your control box is going to turn into an oven unless you're planning on linking it to the spindle water cooling!

This concept is workable if the power dissipation is less, which is likely to be the case for the 24V output, but it seems a lot of hassle and expense when you could have just got a transformer, or two, with the right voltages and VA rating to start with. The only reason I'd do it is if the devices you're powering need the high power quality (low ripple in particular) delivered by a linear supply, which seems unlikely.

Jonathan, Check your mail..

I have...