Member postings for Peter Bell

I'm driving a Nema 17 stepper motor driver with pulses from a voltage controlled oscillator. The motor runs fine at high speeds but when I run at slow speeds ie,20rpm the black driver keeps flashing the alarm light and the motor sounds rough, the open frame one sounds better but at slow speeds the motor makes a ticking noise.

Tried various switch settings for pulses/rev and current and adjusting the input frequency to maintain a low speed but no real difference in the noises.

Is this a characteristic of these cheapo drivers, am I expecting too much or are there smoother alternatives?

Peter

The commercial 240 single to 380 three phase inverters I've seen dont use transformers to increase the voltage they use a voltage doubler and the 650 to 700v dc generated from this is fed straight to the inverter HT rail where the electronics chop it into the three phases as per a normal inverter.

As mike says they will also work if you lose a phase but not on full power, they will also work on rotary convertors.

I use a few standard 380/400v three phase inverters fed with home made voltage doublers producing 650-700vdc and they work fine so long as the switch on surge is limited, I use a 250w bulb and 2 second delay timer to energise a contactor switching the main supply on to the doubler.

Doesnt solve your problem but thats why they are expensive in my experience. Good luck with the transformers!

Peter

Is there a usable or useful Ardunio simulator that anyone has found or uses on the lines of the excellent PE6 which works with the Picaxe chips?

Or is a simulator not really needed with Ardunio?

Just looking around and getting all sorts of confusing signals for a beginner!

Thanks Peter

Thats it, spot on, many thanks

Peter

Arduino topics seem to crop up fairly often and I seem to remember a recent thread which described an Arduino DRO and some updates.

Problem is I cannot find it! It may even have been part of another thread?

If anyone could point me in the right direction I'd be very grateful.

Thanks Peter

Thanks David, just sent pm.

Thanks for the material suggestions, very helpful. I've managed to get hold of a small piece of EN19 and made one. I changed the design slightly to made radiused corners where the original broke at the sharp edges. Its now installed in the hydraulic block inside the machine and so far its now working and giving an adjustable pressure to the clamp (20-120bar) so I'm pleased with the progress. So pleased I forgot to take a pic!

Not sure if its going to hold also I'd like to make another better one just in case so I'd like to take up the offer of the P20, what the best way to arrange?

Peter

Thanks for the replies, good to see the variety of machines that are working with Mach.

I use Vectric Vcarve and if I occasionally want to alter a drawing it takes an age with my existing computer hence the addition of a laptop might improve things a bit.

I've also got an offer of some Ardunio tuition but then I haven't got a laptop so it may be useful for that as well.

Peter

In an earlier post I was trying to find a manual for a Polar 55 paper guillotine which had hydraulic problems. I never found a manual but found some info and dismantled the hydraulic valve block where I found the broken housing which has the valve stem running through it.

As a new part is unobtainable I was going to machine one. The valve spindle is 8mm dia and its about 28mm on the largest dia.

The existing material can just be filed and produces sharp sparks looking like carbon steel. I was hoping to avoid heat treatment.

The nearest material I can obtain is 24T, has anyone a better suggestion for material?

Peter

Thanks for the replies. Its an older Sieg KX3 running with the parallel port on the ancient pc so was planning to go motion control? If that makes sense!

Peter

Thanks Les. I've seen a lot of replies on a similar theme so went for a pc but its getting very old now and wondered what the current situation was as the post is from 2008.

Spoke to someone recently who was doing it all from a tablet with no issues but that sounds a bit far fetched!

Peter

Want to buy a s/h W7 laptop which may (but not essential) run Mach.

I seem to remember reference to a Dell Latitude machine in an earlier thread but cannot find the thread and a bewildering choice out there!

Peter

Thanks for all the input, I seem to have quite a lot of 600v diodes with a suitable current rating in stock so intend using two in series. Seem to have so much stuff in stock better try and use some up!

Peter

Many thanks Murray

Peter

Am I right in thinking that 600piv diodes will be suitable for use with this voltage doubler circuit with 250v output from the transformer?

Thanks Peter

Tried the manufacturer, they were helpful but unable able to give me any info due to company policy--but I managed to get a parts manual out of them.

As the machine is 30 years old thought there might have been some info out there but giving my details to one of those sites fills me with dread.

Ian, Thanks for the offer. We have solved a number of problems and at least its working, but are left with the clamp pressure not being controlled by the front knob, its at 140 bar also the screw which sets the amount knife come onto the material winds itself back from say 1.5 to 0.

Would a PM be better?

Peter

I've been trying to find a technical manual for a Polar 55em paper guillotine I own but all I come up with are sites which appear to offer the manual but you have to sign up first?

Does anyone have experience of these sites---feel a bit wary in case of the usual interweb scams?

Peter

Fairly recently I vaguely remember reading about a DIY low cost magnetic linear scale using a sensor ic and a magnetic strip with multiple tiny north and south magnets along its length.

Does anyone have information on these, was the idea flawed?

Or did I imagine it!

Peter

Thanks everyone, especially the hint about running the fridge upside down on the mains.

There was enough gas in the bottle to run a gas ring for a few minutes so dont think the bottle was completly empty when I exchanged it.

I suppose the real proof would be to have tried it back on the old bottle, if I'd thought seriously I would have taken another, didnt expect it to make any difference!

Peter

Our ancient camping fridge can be run off 240v, 12v dc and propane. Used it last weekend on propane and it barely cooled.

Back home it ran at 50F on propane but 30F on 240v. The bottle was nearly empty so I bought a new one, tried again and its on 28F (flat out).

I'd been told previously that the "quality" of the gas reduces as the bottle empties and the more volatile fractions go first but never really believed it.

Is this true or merely coincidence?

Peter