Eventually this will be powered via a battery, but being a long term project, I'd like to create a simple 24v (ish) psu and start playing with the power draw before I commit to a battery (as weight is a large factor).If it's just for short term testing, you might be able to borrow two car batteries.
Would it be false to assume that there will never be 2 phases on at any time with a controller using microstepping?Yes - microstepping or not.
Ideas:You wouldn't happen to have a large photo copier to strip?
1. buy a purpose built one
these seem quite expensive when i have access to a very large quantity of printer/copier/computer parts
2. series 2x 12V atx power supplysDodgy? how?
all the designs seem to use a floating ground which seems pretty dodgy
3. modify atx power supply to output 24vIf you have never worked with SMPSUs, that would not be the best option (to put it mildly).
most of the info i can find on this is poorly documented at best. it seems doable if you can swap out select components (mostly resistors) and upgrade a bunch of caps, though all ive found simply disable the overcurrent protection which im hesitant to do (or upgrade it, which sounds like a nightmare to calculate since you will most certainly not have the original schem)
4. build oneFirst, a 24V transformer will give you around 32V DC when peak rectified.
A professor of mine recommended using a 24 Volt transformer with a simple prebuilt rectifier/filter caps from canakits.
(http://www.canakit.com/4a-universal-ac-dc-converter-power-supply-kit-ck354-uk354.html (http://www.canakit.com/4a-universal-ac-dc-converter-power-supply-kit-ck354-uk354.html)) (putting two of them in parallel to give me the 8A) (i have what i believe to be a 24v ac transformer, but i can't find the datasheet and as such the max amps. i guess for that matter i have the entire power supply board from a rather large hp 2200 printer which i figured i might be able to just use that damn thing, but again, no spec sheet or max amps)
Is there an approximate method for calculating power requirements for stepper motors? I couldn't find any literature on the net about it.Would it be false to assume that there will never be 2 phases on at any time with a controller using microstepping?Yes - microstepping or not.
You wouldn't happen to have a large photo copier to strip?I should, but I'll have to look around. I recently grabbed a board from a broken HP 2200 printer. I've attached a photo of it. It turns on and I'm able to find some 24V potentials if I look all around it, but I think you have to do something to turn the current at 24V on/up with the relays. Just a guess, but they flip on and off when I used my DMM to check some things when its on.
(They're usually 24V)
Well I've got two ATX power supplys atm (though I can certainly get more of the old dell ones). One is a pretty nice Antec 500W PSU that I just got from my personal comp after black friday upgrades. I thought the newer ones regulated on the 12v. I use my power resistor 'load' setup on he 12v on that guy. I've also got a shoddy (old) 300W dell psu thats prob over 6 or 7 years old. Should I be putting my power dump resistors on the 5V side instead?2. series 2x 12V atx power supplysDodgy? how?
all the designs seem to use a floating ground which seems pretty dodgy
Problem is, that they regulate on the 5V side (And doesn't have that much current to give at 12V without some rebuilding).
Yeah, the 'guides' make it sound easy, but it looks like a damnned nightmare. That and even though I use fuses liberally (man if we didn't have fuses in mechatronics lab....)but I wouldn't like removing the overcurrent pro, though I suppose if you're modding the whole deal, you could upgrade the overcurrent pro.3. modify atx power supply to output 24vIf you have never worked with SMPSUs, that would not be the best option (to put it mildly).
most of the info i can find on this is poorly documented at best. it seems doable if you can swap out select components (mostly resistors) and upgrade a bunch of caps, though all ive found simply disable the overcurrent protection which im hesitant to do (or upgrade it, which sounds like a nightmare to calculate since you will most certainly not have the original schem)
First, a 24V transformer will give you around 32V DC when peak rectified.Ok, the attached photo has a picture of the transformer. I've searched pretty well to try to find it's datasheet, but nothing. So I have no idea what it's rated for. I can run any test you'd recommend. It has 4 leads on the thicker side (primary?) and 8 on the small side (next to the heat sink. Yes I'm aware the leads don't really help in identification). It's got two sets of numbers on it. After looking around quite a bit, I'm pretty sure the logo is Matsushita Panasonic (at least it looks exactly like the second photo for them found here http://www.classiccmp.org/rtellason/logos/semiconductorlogos.html (http://www.classiccmp.org/rtellason/logos/semiconductorlogos.html) ). So it has that [M] thing with the following string RH3-0291 (next line) 011D28IS. The black part on the top says SMTJ35A18T. I can't find anything on the second serial, the first one only brings up replacement parts for the board, not datasheets.
You'll need an 18V (AC/RMS) transformer for getting 24V DC
If you want to regulate down to 24V, shoot for 27..28V rectified DC.
You don't need a PCB for a simple rectifier. I usually solder 4 diodes and a capacitor directly to the transformers terminals and then wires from that to whatever further circuitry.
Your HP supply can be measured to find the max current.
How much does your 24V transformer weigh and what's its dimensions?
Those numbers will give you a rough estimate of what power you can expect it to put out.
Ok, the attached photo has a picture of the transformer. I've searched pretty well to try to find it's datasheet, but nothing. So I have no idea what it's rated for. I can run any test you'd recommend. It has 4 leads on the thicker side (primary?) and 8 on the small side (next to the heat sink. Yes I'm aware the leads don't really help in identification).Oh boy... That's an offline switchmode supply and the transformer is NOT a regular mains transformer!!
[...]
I can unsolder it if you'd recommend, but if I can use the board in part I'd like to avoid that (so I can't estimate it's weight). It's dimensions (of the light grey EI part) is 1.5" x 1.75"). There are several other smaller transformers, but I figured that bigger guy south of the largest cap is the 24V one.
When you say 4 diodes and a cap, you're talking about building a simple diode bridge and a cap to smooth out the ripple? How do I spec out the cap/diodes? This board definitely has IC diode bridges I can identify and plenty of caps.Yes, a common Graetz bridge and a cap.
Also, I just found http://www.mpja.com/ (http://www.mpja.com/) which has some power supplys that a much cheaper than I was finding before. So I might just buy a purpose built one for a bench supply. But in anycase if I can built/modify something for cheaper, that'd be a better solution imo. Self-support college student on a budget and yadda yadda yadda :DThat sounds like a good idea, as I can see that you're out of your safe-zone on this one - and your budget means nada if you kill yourself :)
Oh boy... That's an offline switchmode supply and the transformer is NOT a regular mains transformer!!How does one tell the difference? When I took apart my UPS (the battery was dead) it had a very heavy and large transformer. Prob 10 or 12 pounds and was about the size of an apple. Is size and weight pretty much it?
A regular iron cored mains transformer is larger and heavier (even a 50VA transformer is over 1kg).
Perhaps I should prepare a guide on building a basic PSU when time permits.
That sounds like a good idea, as I can see that you're out of your safe-zone on this one - and your budget means nada if you kill yourself :)
The http://www.mpja.com/24V-10A-Hengfu-Power-Supply/productinfo/18436+PS/ (http://www.mpja.com/24V-10A-Hengfu-Power-Supply/productinfo/18436+PS/) should suit your purpose.
How does one tell the difference? When I took apart my UPS (the battery was dead) it had a very heavy and large transformer. Prob 10 or 12 pounds and was about the size of an apple. Is size and weight pretty much it?An Apple computer or...?
Alright final stab at saving budget. As you recommended I was able to grab the main ps board from a prob 4-5 year old large multifunction copier. It looks much more promising than the old board. I've attached a photo of it.The rectangular black thing in the lower right corner might be a relay (hard to see) and if it is, it's probably what's clicking.
(The blue/red wires go to the original power switch.) I can hear something click when I turn it on, but I can't find any voltages on the output pins (see the second photo, these look very similar to motherboard connectors and each pin is labeled (!!) .)
Now I'm assuming you need to ground a logic pin or two to turn the output voltages on. (Also, looking at the top right, it has the input and output voltages AND amp ratings (see bottom of second photo). The ratings look to be perfect for what I'll be wanting to use it for.) Any ideas on turning the rest of this guy on? :DIt may be that some of the connectors are for control logics, but a copier supply will have a large number of sub-systems each needing power.
Thought so.I suppose I should check the fuses first.Fuses are good. Now, there are some curious things written on the board. The bottom left has as large 24v relay, which looks like it might be the key.
The coil pins (well two pins, which from the data sheet look like they should activate the relay) go to one of the small connectors (CN113 in the photo, top left) and are labeled TRELAY and T24V.You have a datasheet on the board??
There has to be something simple with the smaller connectors that makes the magicNo, that's made by fairies and lepricons.smokehappen.
Random question: There's a plate that covers the top that has a transformer looking like object attached to it (its the yellow/grey metal object resting on top of the center heat sink in the first photo). It only has two wires though and its connector pins are not labeled. What the hell does this thing do? From my meek EE221 knowledge, this could only be an inductor? Transformers need a minimum of 4 wires no?Random answer:
So, bring me some good news so I can wrap this puppy up in a grounded box and call it a day :DBring me the datasheet and we can try :D
P.S. Super thanks in advance. I'm sure you get tired of schooling newbies on how to not kill themselves.You're welcome - my next tut will be on making a hangmans knot on a solid rope ;D :P ;D
TRY (transformer relay?)
HLT1
ZRC
HLT2
DOS
SW
GND
TRELAY
T24V (these two pins go to the coil of the transformer in the bottom left, no shit, k)
GND
GND
GND
24V5
24V5
24V5
I was able to find some 5 and 5.1 voltages around there somewhere but I don't remember what I was doing then.Maybe the 5V is on at all time when the board is powered - usually it's so, as it's used for standby mode and the 5V logic turns on the rest when the copier is summoned to do its magic.
CN113 pins:And there's no other connections to the relay coil?TRELAY
T24V (these two pins go to the coil of the transformer in the bottom left, no shit, k)
Some of the other connectors have pins labeled 5.1Vcc1 5.1Vcc2. Vcc means the collector (+5V or w/e it requires) for a transistor no? Maybe these control the voltages sources?Vcc is a term used for positive analog voltages - named from the widespread use of bipolar transistors in analog (which for the NPN will have the collector at its most positive potential), while in digital circuits, the positive voltage is named Vdd (named from the FETs drain). The negative equivalents are Vee (analog, emitter) and Vss (digital, source) respectively.
So, I guess I need to play around with it.Yes.
Also, thoughts on discharging the large cap? I was using a motor, but it arcs which is bad. I've been using several resistors (a 2k one then a 1k, then a 250) to bring it down. Is this horrible for the big cap? Fast discharging = cap death?Use around 100 Ohm per volt - for a 24V charged cap a 2.2kOhm resistor will be fine and for a 120V charged cap, 12..15kOhm will do (but then use it in a way that isolates it from your pinkies and similarly sensitive stuff :)
Update: Got it! Apparently using a screw driver to short the SW pin to GND was a poor method. I guess it needed to be fully on at power up. Shorting this pin makes it all work.Great :)
I'm still not sure what the relay is really for. I don't think I need it, but we will see. It's currently removed.Maybe it routed mains to some other part of the copier, but it would make more sense if it powered up something on the PCB.
It's a SPDT relay and one of the throws is mains voltage but I can't figure out what the other one is. In either case the supply seems to be working fine (at low current anyway, I'll doing some heavier loading tonight) without it. If that relay takes 24V's to activate, would it really make sense for it to 'activate' some high current side of the board? I boxed the whole deal up so I could have it on my bench and not be worried about all the exposed things and whatnot. I attached a photo for S&G.A functional box! (Isn't that a nice way of putting it ;D)
It gives me 2x +24V (each at 6.3A assuming the fuses are correct, total of 9.5A), +12V (0.3A) , -12V (0.1A), and +5.1V (5A). So I think this should work perfectly. The whole box is grounded sheet steel and from my minimum tests last night, everything seems to be working. So thanks for your help Soeren. :DHey, you did all the work :)