Baie mooi Kobus.
I see you are working with ply mainly.
I will have to move away from the MDF as well. It looks like I am allergic to the dust or the wood. Not sure. I am full of little blisters for months now.

Johan, you should move back into the house now that your MM is up an running...stop sleeping on the machine. :D

I hate MDF as well, lots of dust,,,,,bad dust,,, and this stuff is really not that strong.

The SHUTTERPLY I am using is also a lot cheaper than the MDF for the same thickness. I pay R 220.00 for a sheet of shutterply.

It also seems to lay FLAT on the table..much better than MDF

Where are you sourcing that shutterply? I am paying about R175 per sheet here in CT but the quality is not anywhere near as good as the ones you have used so far. Lots of knots and open cracks in the face plys.

Kobus the only thing with ply is that we don`t get a good quality ply, and shutter ply can be very rough sometimes.

I bought some from Builders W/house...very nice quality overall...must be imported, because the local Sabie stuff is rubbish.

Just got a number from a chap in Primrose (close to my work) that has a LAMINATING shop. He made up 18mm ply for a friend...this stuff is magic.

Kobus,
Don't you find that the shutter ply pulls after you cut the job?

I miss that luxury of having those suppliers around me.

I have not noticed anything yet Marius.

My little lathe is commin back to life. Assembled it tonight.. I need a favour from the electronic guys on the forum... I need a circuit for an electronic speed control: Spec...DC 25 - 220 volt and no more than 2 Amp. Thanks

Attachment 10208

R1 100K ohm
R2 10K Ohm
R3 100 Ohm
P1 pot 1M Ohm
C1 capacitor, poliester 39-56 nF, 400V
C2 capacitor, ceramic, 10nF (mark 103)
C3 capacitor, 100nF, 630V (marked with 150nF on shematic)
Q1 triac, TIC216M, 6A, 600V, 5/10mA
D1 diac, BR100/3, 32V

I used this to speed control my little trim router, be very careful with mains voltage!

http://www.md-tim.com/mechmate/speedcontrol.jpg

Good circuit, but the motor in question is DC, not AC. You could add a bridge rectifier to the output, perhaps?

My mistake, I have not seen that the motor is DC

No problem as long as we get there in the end. That little late must run by Saturday ;)

DC motors are not controlled by that kind of circuit. You need a PWM (pulse width modulated) controller. I have been out of the electronics world for to long to help you with a circuit and PWM stuff is a little more tricky. Try http://electronics123.co.za/ for PWM kit. Dont use a regulated power supply as this will not give you linear torque over the range. A PWM motor controller is best.

Actually, Marius, that looks like it is a PWM circuit. Specifically, it uses 2 X the line frequency. The Triac turns off every 1/2 cycle as the AC voltage crosses zero. It doesn't turn on again until the resistor / capacitance network charges to a sufficient level, effectively giving you pulse-width control.

However, the output is AC. If you rectified the output, and perhaps added a capacitor to smooth it (slightly, not too much or it won't respond to the control), it looks like it would drive a DC motor.

I've been musing on how to solve Kobus' problem. The mains voltage is 220 there, right? The simplest circuit would involve just rectifying to DC, then adding a motor controller. Unfortunately, most motor controllers don't like voltages higher than 30 or 50V or so. So now we're talking about building a power supply first, then applying a motor controller, which could be H-bridge based like an LM18200 or LM18245.

Another (unidirectional) approach could be as simple as a single MOSFET and a timer circuit (NE556 comes to mind). The MOSFET could be chosen to run at 200+V, although you'll still need to come up with a power supply for the 556, perhaps using a simple voltage divider circuit.

Kobus asked for a schematic, so presumably he wants to build his own as opposed to buying a kit.

Kobus, what do you want? uni-directional? bi-directional? Do you care if it's a kit over a schematic? Do you have a large electronic parts drawer?

Thanks Brad, Yes I would put it all together if somebody does the design. I can get a Mosfet IRF 840 B that can handle the high voltage. Bi-directional I will do with a SPDT toggle switch with a Centre OFF position after the speed control. So basically all I need is a circuit schematic to take the 220 volt AC and give me a 25 volt - 200 volt DC output by means of a control pot. The logic supply can be done with a simple circuit or a small mains adaptor.

Here's a design (I haven't tested it, obviously!)

You'll need a motor power supply up front of it to produce 200V DC for the motor, and then a logic power supply.

The motor power supply up front could be just a bridge and capacitor ( 220v * sqrt(2) *2 / Pi is 220v * 1.41421 * 2 / 3.1415926 = 198 V). Don't forget to fuse it well, and I would prefer to have a transformer in there, even if 1:1 to limit current.

For the amount of current the 555 and the mosfet gate need, you can likely just use a pair of 1/2 watt resistors as a voltage divider. With a 10k resistor from the 200VDC and a 470ohm resistor from GND, you should end up around 9V to drive the oscillator.

As always, someone check my logic and math, please!

I see that N-Channel Mosfet is only 55 Volt. Suppose I can replace it with the IRF840B that I can get over here.

Kobus,

How about one of these:

http://www.varispeed.co.za/modules/D...show&id=MTI%3D

I used one on a ring roller, slow, fast, forward and reverse. You do need a 3-phase motor, which is cheaper than a single phase in any case and a pot to regulate the speed.

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?