Kobus

I'm not that flash with electronics but as posted previously it looks like a chinese model similar to the one I have, the is a yahoo group for these things (called 7x12minilathe) with plenty of information on exactly what you are discussing and many people with more knowledge of these things myself (I believe there is a circuit concept for a speed controller also) I'd suggest this group would be worth a look.

Jed

Kobus can you use a bench drill press with the pulley`s? (to reduce speed) that way you don`t need to sukkel with electronics.)If yes you know where my dad stays. there should be two one working and one where the motor packed up or probably needing a cap.

Thank's Hennie, but that setup will be bigger than the lathe :D

I will push through with the electronics...am sure I will get it going.

I meant to post my comment much earlier on this DC speed controller thingy, tried to put up those info I kept aside for moments like this... ;)
but I failed to find the circuit for it. I am positive I kept some useful circuits somewhere... but no luck finding it.
Anyway, for DC motor speed control, PWM is what modern electronics guru will use...
& in this age of time, microprocessor seems easy & cost effective for the purpose. Have a look here
and here
here

Thanks Ken, but most of the circuits are for low voltage and low current. Like I said I need this thing to go from 25 volt DC to 200 volt DC.

The trick is in the power transistor... you can use the micro processor to generate the PWM necessary & then use a mosfet or something which can handle 200Vdc (which is common) as the current amplifier, that should do the trick.

Kobus, in the design I pointed to above, you would replace the MOSFET with one that meets your needs (N-Channel). The IRF840B seems appropriate. As Ken points out, you simply need a source of pwm pulses that come in at somewhere between 4v and 30v (the MOSFET gate switches on between 2 and 4V, and can survive up to 30v).

You want to control the source with a simple knob. The approach I pointed to above uses an analog timer-based oscillator circuit that is directly controlled by the potentiometer. A micro-processor based approach would do an analog to digital conversion to get the value of the knob, and then use software to convert that into the PWM signal on an output pin. Inserting the micro-processor gives an opportunity to vary the characteristics of the PWM using software rather than component parts. It's really just a question of whether you want to spend your tweaking time at the bench adjusting electronic components, or at the desk debugging software.

If you do build this, please be careful. That's enough voltage to hurt running around that circuit board. Don't forget to heat sink your MOSFET!

So the four building blocks are: high voltage DC power supply, low voltage DC power supply, PWM pulse generator, and power switching stage (MOSFET). You've got choices for each block.

Hi Kobus,

The controller you need is a single quadrant (1Q) SCR based controller. Bongfiglio has them but the price might not appeal to you(?), probably over R1000. I have a good design but it requires a double sided PCB and some PT which might not appeal to you either. Saftronics used to manufacture them too but I don't know if they still do (or if they are even still in business), I have never seen a kit of such a design (SCR based). There are kits available using a thyristor (Velleman) for probably around R400 and they would work well.
Greg

Thank's Greg, but I think I am sorted...will know this afternoon IF our Postal service make good on their promises of overnight delivery.
I spoke to my brother-in-law that gave me the lathe. I mention that I am having difficulty in finishing the lathe as the controller is missing. He then suddenly remembered that there was some sort of box with it when he bought it on the auction. I asked him to check if there is a PC-board in it. He came back and told me that there is a PC board, toggle switch and pot.....Everything seems complete.
When I receive it, I can check if it works, if not it should be a simple matter of fixing it.

Well, the Post Office delivered on time. I could not wait to get started.

Stripped the PC board out.....had to fixer out all the loose wires.
Attachment 10245

Plate indicating Machine details
Attachment 10246

Looks like TYN410's doing all the hard work

Attachment 10247

And there she is....all cleaned up, polished with all the parts back where they belong. Have to replace the 5k POT with a new one that has a knob. Then a nice sticker showing ON/OFF FORWARD/REVERSE etc.

Thanks for everybody that tried to help.
Attachment 10249

I promised that I will have 2 chairs on display at our annual Woodworking Fair next Saturday in Benoni. So today I had to finish them. Also fixed the rocking chair as we forgot the bottom supports on the seat. All done and ready for the fair.
Attachment 10258

With the help from old BBB is was easy work to make 2 chairs...and they look the same ..

These chairs are a bit wider than normal....just for us NORMAL big people.

Excellent job man.

Nice Chairs Kobus. Are they your design?

Thank's Marius. Please send my your new e-mail. by PM

No Heath, I borrowed a set of templates from a friend and made that 2 seater bench for my friends wedding a while back.
I then went and put in V-Carve Pro, now I do all the pockets and outlines and it is then a matter of putting it together.

I wanted to make another bench, but after planing the wood I came in under 20mm thick. I then decided to make these oversize chairs rather than a bench.

At the Woodworking fair last weekend I had a lot of interest from potential clients. One of the first jobs...that had to be finished by this weekend.... was this plate to celebrate a 60th anniversary. After I finished it last night, the client requested I make the stand as well, so this afternoon after work I quickly designed the stand and cut it from MDF.

Sorry for the poor quality, but my camera battery was flat and I had to use a cellphone
Attachment 10286

Gee hom gas Kobus.Ek kry terugvoering van die verskering later in die dag,ek hoop net nie ons goed staan vas in daai verkeers knoop in China.

How very insincere of you Andrew - go sell your stuff some where else SPAMMER.

Ross,
What do you smoke mate, your message makes no sense!!

Hi Marius - I am a victim of retrospective editing of the post. A spammer who has advertised four times on this forum by posting links to a furniture store, posted a link selling furniture once again.

Did I imagine this? - here is the original text

Looking Nice stuff .
Spacify offers sparkling contemporary dining table, contemporary dining chairs, upholstered dining chairs, Italian leather dining chairs, contemporary dining furniture and contemporary dining tables.
upholstered dining room chairs (http://www.spacify.com/contemporary-dining.htm)

I was a bit dirty with spammer "andrewjones" as I really enjoy seeing what Kobus has made and did not enjoy him leveraging his own business off such an interesting thread in such an insincere way.

Regards
Ross

Ross,
I take note, I did not see any spam on my side. Does he send it to your private email or is it on the forum?

Hi Marius

It came through on my email for a subscribed link, then was also visible on the forum momentarily.

No problem at all, people are always telling me I make no sense. I'm quite used to it actually. hehe

Regards
Ross

Ross,
Making sense has nothing to do with the creator of it but with the receiver thereof. I am sure things always makes sense to you. Makes you wonder.

These days the crooks are much more creative than us normal guys.

Marius, Ross,
Mike or moderators will keep the spammers at bay, but sometimes others posts do not get cleaned up right away. Check back a few weeks from now and all this might be cleaned up. :)

House keeping complete SPAMMER eradicated :) .. ie bant for life.

Looks like I missed all the action :eek:

I finished that little Mini Lathe.. Ended up building a new driver working at 110 volt. My boss was so impressed with it that he made me an offer I could not refuse.....sold the lathe to him.... handsome profit.:D

Found this bigger one...850mm between center with a massive chuck. Motor mounting plate was missing and the slide handle did not move the carriage left or right.

Made a new plate, wired up the 2 x cap motor , opened the gearbox and found one gear has broken the shear pin. Fixed that and now it is working like a charm.

These lathes were built in South Africa under licence from Angelini Vittore by the 600 company.
Attachment 10386

Attachment 10387

Attachment 10388

Since old BBB is waiting for his new computer...buying through my brothers computer shop... the neighborhood is quite.

This weekend I got an order from the BOSS to make a table for one of the rooms. Just to show that one NEEDS a CNC router, this is what I came up with...no curves, no shapes, just a BASIC rectangle table with square legs....BORING....

So for anybody out there still wondering if he or she should build a CNC Router....GO FOR IT!!!!!
Attachment 10519

Hi Kobus,
Very proffesional looking! Hardwood does make a good looking piece.
I admit that I do not have a lot off knowledge on furniture manufacturing.
Did you do the top on old BBB -completely - including the frame corner miters?
And did you dowel the top of the legs to the fame(skirting)?

No Johan, like I said..BBB is out of action and everything was done manually by hand and workshop tools. A while ago I made a MITRE SLED with my MechMate and used it to cut the mitres. The legs sit in the corner of the skirt and is supported with triangle blocks both sides.
The Blackwood sides are joined with Biscuit joints to the Matumi main piece top.

Remeber old BBB is just a tool and its how you apply that tool that counts, Looking at that table, you seem more than capable of applying all your tools - the manual and computerised types. Getting 4 accurately mitred corners around a solid wood center panel is not that easy - something you have appeared to achieve without the help of the little blokes running around inside your stepper motors :)