32 replies to this topic

[sasman]

Well the actual running of the cell i will post in another thread..

If done correctly there will be hardly any waste ..Waste = money lost .. im only making small amounts..I have read countless patents spent literally 100 hours reading on the subject and , i have all the tools required to make some very pure perc...All i need is a good relable power source that will last ...

The only waste wil be the chlorate destroyed chemically..which will be a few grams per litre.. this is not very great..every thing else will be recyled ..

The PSU will supply 3.3V hopefully even if i cant increase the voltage high enough to make perchlorate , i may be able to make chlorate...i have read some patents were they use a low 3V, 3.3v will probably work just have to wait and see...it all depends on the voltage drop in the cell...
My HAM radio friend says that there will hardly be any voltage drop if useing 100 amps..from a 400 amp rated supply.

.Also as for is it worth it argument.. i totally agree.. if i could buy it as cheap as i will be able to make it i would ..Also there is the satisfaction you get from doing it your self..another thing is consistancy.. if i do a good job my results will be repeatable ,that = success..= saftey..

[Andrew]

That PS looks like a real winner, hope all goes well, I'd really try that ADJ pot and see how much it actually adjusts the output, I suspect it will be for fine tuning, but worth a try. The internal circuitry could also be "looked at" , but If your not too keen on doing it yourself, I'd suggest getting a friend to do it. I'm sure a PS of that caliber will have well rated componants that will not mind being run at a higher voltage. The job might be a bit complicated to do, because I think that you'll be lucky if you only have to change one thing. On the other hand, there is always a key point to all regulation systems. Good Luck, remember to leave it switched off and disconnected for at least 15 minutes before opening it up.

Just one other interesting thought, it would cost you around ?500 per month to run your cell 24/7, to make that econmical/profitable, you need to produce at least 50kilos a month, is that a likely posibility?

For the record in defence of voltage doublers, they are very efficient if engineered well and suited to the application. Also all the diode based configurations I know of, work with both AC and DC. It is a common misconception that they are for AC only. I have achieved several thousand volts form a 30volt DC supply before. I have designed a reverse isolating supply capable of sourcing several amps at a voltage above the supply rail using a voltage doubler, the design was required because a switcher was too big. Their effectiveness is very often dismissed and concidered usless in practice.

[sasman]

I just found another transformer..The only problem is that its AC ..I got it for Perchlorate production ..

The output voltage is 6, 8, and 12 v AC..The Voltage i will need is 6V DC..

I got the transformer because its supposed to be rated at 83 amps..However the Label pic.. is hand written?..and when i took the top off and looked inside i found this Big fuse pic..which is rated at 63 amps? yet if i looked at the fuse rating it says 40 amps at 550vac? Fuse rating pic..

Its pretty heavy at 18 kgs...look Inside pic and there is nice thick wire so it can carry heavy current .. inside there is also 1KVA printed on the board..Is there any way i can test to see what rating this PSU is?..

I cant understand how such a big fuse is only rated at 40 amps? i have a 400 watt computer PSU which is rated at 35 amps at 3.3v.. and its only got a small fuse?..

I would like to draw 75 amps at 6 V dc..just not sure what rectifier to buy, you can get 40 amp rectifiers at a few ??? but if you go over 40 amps the prices shoot up!!.. if i need full wave rectification i need 4 rectifiers which sends the cost upwards..Will i be able to use 1 rectifier?..

[ProfHawking]

what i would prob do is use a bridge rectifier and a nice fat capacitor to smooth it a bit.
This is a nice 100A bridge rectifier, but its ?76
http://rswww.com/cgi...stockNo=1837308

You might be able to link up a few of the cheaper smaller ones like use 4 of these
http://rswww.com/cgi...stockNo=1834129
only ?3 each.
Problem is if one has a lower internal resistance than the others it will take too much current and overheat. I think you might be in trouble if that happens. I know ive blown up these things, basically doing what you are doing. It can get messy (and they stink!)
?80 is a lot to fork out tho. could have shipped loads of perc from that swedish company?

[Andrew]

check these out, 4 or 5 in parallel would do the trick, they are cheep, metal cased so heat sinking is easy should you need it and with normal tolerances allowing a 25% duty margin is adequate.

25AMP

35AMP

IF one does blow up, they are cheep as chips to replace and after one or two you will have a fairly well matched set, trial and error causes evolution. If one is not good enough it gets thrown away. I personally never really bother with RS, they are usually twice the price of rapid.

[sasman]

Thanks for the help...I dont like the sound of rectifiers going POP!!..I have looked around and just bought some 400 amp rectifiers hopefully they are the correct rectifiers..

http://www.onsemi.co...40030CTL-D.PDF


I was going to do with half wave rectification but ill go with full wave..this needs 4 rectifiers..so the load is spread over 4 should make it last longer?..Hopefully i should be up and running in the next week orso..

[Arthur Brown]

Note that those rects are on a live base and need a heatsink and specified torquing down in a bridge you will need 4 rects and 4 isolated massive heatsinks

[chrissw]

Thanks for that alany..

i have just purchased his ebook only cost a few $ and will have a look later..first glances looks very promising ..

Would it be possible to connect say for eg... 5 computer atx psu's  each supplying 20 amps in parallel so as to produce 100 amps?.. i have a funny feeling doing that would end up with a big banG!

[chrissw]

Thanks for that alany..

i have just purchased his ebook only cost a few $ and will have a look later..first glances looks very promising ..

Would it be possible to connect say for eg... 5 computer atx psu's  each supplying 20 amps in parallel so as to produce 100 amps?.. i have a funny feeling doing that would end up with a big banG!

You can connect several PSU's with identical DC output voltages in parallel safely if the output from each one is connected to the anode of a 20A rectifier diode and all the cathodes from the diodes connected together to form your '100A' output terminal. What will happen is that the PSU with the highest output voltage (even if they are all say 6V outputs, each one will have a +/-5% tolerance, ie they will not all be exactly identical) will try to supply all the current, causing it's output voltage to dip a bit as soon as it hit's it's 20A limit, the one with the next highest output level will then 'kick in' and begin supplying current. This will happen until they are all delivering current and a sort of output voltage equilibrium will be reached. For diodes, look at either Farnell or Maplins on line.

[sasman]

Thanks Chris but i am not using computer PSU..For power for the cell...I'm into deep using my 83 amp transformer...

Its easy for a project to start swallowing money... and thats what is happening ..The 83 amp transformer ended up outputting AC so now i had to get some 400 watt rectifiers more cost..then i asked for help on Sci.electronics.basics.

http://groups-beta.g...106831492d62b99..
Some very Helpfull people on there...

One says i need a 5 to 10 amp variac so i just managed to get a 15 amp variac at another ?100( i will also use this for controlling my Rpm for my new star rolling machine) ..so the cost is slowly but surely climbing up and up.But once you start spending money were do you draw the line....Hopefully if every thing works all i need is a 100 amp meter DC meter..and may be an AC ammeter to measure effiency of the cell and thats it..

[sasman]

I just received my 0 to 199 amps Digital Amp meter from USA . it came with its own shunt...Ebay 0 to 199 Amp meter.. Very pleased with it.So now i can accuratley measure the current im passing through the cell...

I have had a bit of bad luck with my Diode rectifiers... ... The first 400 amp diodes i bought from Ebay ..never turned up must have got lost in post( seller gave me a full refund tho..)...So i bought 8 110 amp rectifiers from a USA surplus shop.. which came last week ... ..

But when my mate looked at them he said there the wrong type F*@K!!... they are silicon control rectifiers?? ..which he says is no good for the job .. Now even tho i have a 400 amp 3.3 v supply . i have no good way of controling my current .. the only way i have is to use thick Kanthal heating element wire as a variable resistor..which is a bit of a bodge..

So when i saw a 320 amp PSU for sale on ebay i had to have it.. It had variable current control which is what i was looking for..

Power 10 P62BFront and here's the Back..

The guy said it is continously rated and made for 24/7 operation so hopefully it should be ok...

I have for now put my other 83 amp AC transformer on Hold...I want to spend time making Pyro... not pratting about with electric thingy majigs..

So thanks for the advice...but basicaly if your Thick when it comes to electronics Buy one ready built ... ..

[alany]

That's a very nice supply. I've seen such units on eBay, they are ideal for electrolysis work.

If you decide to finish your other supply you can use the SCRs as diodes with a little external circutry to drive their gates. Basically a resistor and diode that makes them fire on the +ve going cycles, they will block the -ve cycle themselves. In fact if you've got SCRs then you are set for phase-angle control of the output of your PSU. SCRs are almost exclusively used in high power equipment instead of diodes, especially 3-phase plating rectifiers.

This site is a gentle introduction to using SCRs:

http://www.allaboutc...3/chpt_7/5.html

You need not spend lots of a special meter and shunt either. A shunt for measuring the current can be made from a length of wire, even just the wiring from the rectifier to the cell. A simple digital meter or a d'Arsonval movement can be hooked up across the shunt and a series pot used to calibrate it. The 10 A scale on your multimeter is sufficient to calibrate a 10000 A shunt if you have a multimeter with good calibration between mV and V.

For smaller cells I'd just stick to paralleled AT PSUs, they are cheap as chips.

[sasman]

Can some one answer this question? I have a variable power supply i can control the current and voltage .

If i short the wires so its got a dead short across the positive and negative output wires turn on the PSU set the max voltage to 5 v and then slowly turn up the current should i be able to load the PSU with out damaging the unit?..

I have done a small test using Nichrome wire as resistance but the max current i could get was a poxy 20 amps.i get more than that out of my old computer PSU?..At this moment i am a bit pissed off i cant understand why this PSU is not giving out more current?..


Thank You

[Andrew]

Can some one answer this question? I have a variable power supply i can control the current and voltage .

If i short the wires so its got a dead short across the positive and negative output wires turn on the PSU set the max voltage to 5 v and then slowly turn up the current should i be able to load the PSU with out damaging the unit?..

I have done a small test using Nichrome wire as resistance but the max current i could get was a poxy 20 amps.i get more than that out of my old computer PSU?..At this moment i am a bit pissed off i cant understand why this PSU is not giving out more current?..
Thank You

There are a lot of factors to consider here. usually on a PSU you set the voltage (as a constant to be regulated) and the maximum allowed current. If this is the case, when you turn it on the current will hit it's celing and the voltage will drop, and the current becomes the constant. By increacing the max allowed current the driving voltage will rise until it gets to the 5v, and then as you can imagine, the voltage becomes the constant. The reason for having a current limiter is to protect against accidental shorts, and to protect equipment from getting damaged.

On the second point, remember V=IR. 5V and 20A means Rtot = 0.25ohms. The internal resistance of the PSU is likely to be around that, well it sounds like it anyway. Using the Thevenin equivilant circuit and a couple high power resistors you can easily measure the internal resistance. Once you know this you can jack up the driving voltage to compensate. Alternatively, in true style, you can connect it straight up to your cell and twiddle knobs until it is right, (start at the lowest possible values though). Also nichrome is well known for it's strength at elevated temperatures, that is why it can be used very thin. Thin wires = lots of resistance, it may be worth checking the resistance of your length of wire.

[sasman]

Well i am getting desperate.. ..I have connected it up to a test cell and all i can get is a few amps!!.

.I then connected a 2mm thick copper coated welding rod on to the output terminals and slowly increased the current.. it got to about 30 amps and began to glow red hot the current then dropped slightly to about 25 ish amps..that was the Max current i could get out of the unit ????..

I then tried a 10 mm bolt across the terminals and this time i got over 100 amps before i stopped the test...so the power supply can supply high amperage...So i am baffled at is why wont it send high amps through my cell?..

I am getting a bit pissed offf with this project...i won some Titanium sheet last week on ebay for use as a cathode and that has been lost in the post.. also lost in the post was my 400 amp diodes(i did get a refund tho..).... this project seems to be jinxed..


I need some way of forcing this PSU to give a fixed current? is there an easy way of forcing the current thru the electolytic cell?...