HW: Leveller Evo (name pending approval by Dave Mac)

[JamesDavies]

So starting work on a new HW. Might take a while as I'll be doing it on free weekends.

Wondering if anyone could recommend a speed controller- the stall current of my motors is around 230A. I'm looking to keep it cheap if possible (student budget) but prepared to fork out a bit.

Possible designs uploaded soon.

[maddox10]

A Wotty.

[JamesDavies]

What are the max amperages on the 360?

[maddox10]

Enough to survive your motors.

[geeza]

360amps, don't scrimp on the speedo you will suffer down the line if you do. Wotty is the best bet yes.

[maddox10]

A good speedo is an investment for years. Especialy a speedo with good support.

[JamesDavies]

Cool, I'm happy with Wottys. Do second hand 360's come up for sale often? Or would it be better to get the 360EVM new from Ian?

[JamesDavies]

Also, are burkets worth buying second hand or is it best to buy new?

[maddox10]

Not often that they turn up second hand, and in most cases, those need some TLC like replacement seals. If the solenoids ain't AC .

[daveimi]

I don't own a pneumatic based robot, but I would have thought from a safety perspective new valves would be a must.

[JamesDavies]

Ok thanks. Where is the best place to get them?

[maddox10]

We buy our Burkert 5404 1/2bsp 24V DC coil 2/2 valves with RS components.

But there is a less expensive way, if you're willing to go Chinese. 2 disadvantages. No warranty whatsoever, and except the body, not compatible with the Burkerts (means you can use an original burkert body, but have to replace anything else if you want to mix and match). You can buy 5 "Churkerts" for the price of 3.5 originals. And that's including import tax. (why 5, because that's the minimum)

[JamesDavies]

Thanks for the info. Very helpful.

I'd like to understand before I buy- this valve (the 5404- I assume the same as the one you are referring to?) says it is good for pressures up to 50 bar. I thought the fire extinguishers produced about 60-70 bar? Am I being stupid here?

(link to valve: http://www.buerkert.com/COM/buerkert...e=5404&sk_id=2)

[maddox10]

The firm "Burkert" garanties that the valve will work constant and dependable @50 bar with a working voltage of 19-24V, what a standard PLC voltage is.

In the 13 years I use those valves, and a lot of roboteers with me, we learned that the pressure isn't a factor, and that the valve can withstand 200 bar(thanks to Mike Lambert, who spend the money to have them certified). The point is that it won't work always unless you feed it 24V+.
That is why we use a voltage booster in our feathers, meaning we don't have to lug around a 24V battery.
In the heavies we run 36V, so there it isn't an issue whatsoever.

The only disadvantage of 36V on the 24V coil is that it will run hot. But with a working time of 5 minutes max, the solenoid , ment for permanent powering, won't care.

Things that will ruin a 5404 are swarf and age.

[JamesDavies]

Getting this back on track again- I'm wondering what batteries people use? I dont think I'm ready to go full LiPo yet, but I think I need to finally upgrade from SLAs.

So-

What NiCads do/did people use? I'm hoping they will provide me a middle ground...