Minit lathe - can you help ID my wiring?!

Man I love this site....my Sieg lathe board is nuked, I post here accordingly - John S put sme onto a dirt cheap replacement on Ebay that I'd never have found/considered ...it arrived today with no documentation (& seller not likely to have any) , I ask for help & within an hour or so, I have the full documentation (that not even the manafacturer could furnish me with!) - great stuff.

Thanks guys! :beer:

** Looking at the maual I'd have likely blown it to pieces as it's got some recommendations that I'd gave actively done the opposite - eg ...don't ground the switch or speed pot, etc! (my sieg board switches are grounded)

Good im pleased for you :beer:, reciprocal love !

Ok, I'm on the home straight ...I just need a sanity check re the DC motor connections & the 'current sense' resistor.

Firstly, I reckon the DC motor connections are A1 & A2 on this diagram (there are spade connectors marked as such on the PCB)...

http://img9.imageshack.us/img9/2937/wiring1w.th.jpg

(John S, confirmed that on the original Sieg board that A1 & A2 are the DC Motor connections & I gather this must be a standard naming convention, but those F1 & F2 connectors are messing with my head!)

Ok, next challenge' ....current sense resistor! This board talks of having an external current sense resistor, but if you look at the chart, it seems ludicrously low...

http://img12.imageshack.us/img12/7127/wiring2z.th.jpg

my motor is 250W, which apparently is 1/3rd of a horsepower - therefore looking at that chart it needs a current sense resistor that is 0.027 Ohms - are they having a laugh?


Where on earth will I be able to source a resistor such as that? (Danfoss apparently don't make these driver boards any more ...not sure if Graham do) ...since the resistor is in series with the motor ...it's going to have to be able to handle a fair whack of current...therefore I'm figuring it'll need to be able to disappate a fair bit of power too?

Has anyone experience of such current sense resistors? Is there a 'frig' where I can do away with the darned thing?

Many thanks

No the resistor should only have to dissipate 0.5watt.
so at 4 amps and 0.027 ohms then 4 x4 x 0.027 =0.432 watts.
You may have to parallel some to get near the value. Just did a quick search so far nothing in uk.

Peter

just found http://cgi.ebay.co.uk/Vishay-LVR05R0...3286.m63.l1177

so should be available in UK

Thanks Peter, I couldn't find anything (well nothing less than £10 - for ten resistors...eeek!) , so I paniced, then got creative & 'rolled my own'. I happened to have some 29SWG enamelled copper coil wire lying about ....& I worked out that two strips of 31cm in parallel equals about 0.027 ohms, as apparently it's 0.173 ohm/mtr at 20C), here's a pic of the result....

http://img25.imageshack.us/img25/7835/17341875.th.jpg

& it actually works! My lathe is finally turning again!

Ok, so here's my final 'puzzle'

I've wired in a 'normally open' chuck guard switch provided (working on the theory that being new to lathes, if I don't have one of these I'll definitely end up with a chuck key in my cheek).

For the life of me I can't figure out how it can be 'triggered' (I only received a 'box of parts' from the seller)....there doesn't seem to be any cam/'sticky out bit' (technical term or what?!) on the chuck guard that can activate it the switch lever. Worse still the screws suggest the lever switch goes face down into the plastic recess hown in the photo below - that doesn't compute as there's no way in hell it can be 'activated' then!

If anyone has a mini lathe with a chuck guard switch setup similar to this, I'd really appreciate a photo/explanation of how it all fits together!

http://img19.imageshack.us/img19/5535/switchb.th.jpg

Rob

Firstly you only need to use terminals marked F if you have a shunt wound motor, I am assuming that you only have two wires coming out of yours if so you just use the A marked terminals.

The sense resistor is used in some drives as part of a feedback circuit to limit the amount of current the motor can draw, and help prevent your motor from burning out, it can also help out with low speed torque issues, this subject can get quite complex so we'll leave it here!

Anyway this rs part number should help you: 199-6356 it is for a 0.03 ohm 6W resistor which is just about right for you. As peter correctly says your dissipation will only be about 0.3 - 0.4 w.

You posted while I was typing, glad you got it going Rob.

Dave

Hi I have some 0.082R 3% 10watt resistors they were pulled from some large redundant PSU’s. If you have the room to parallel them up, you are more than welcome to some for the price of the postage.
Ivan.

Hi Ivan,

Thanks for the kind offer....what I've 'lashed up' seems to be working & there's not a great deal of room in there (I actually had to push my coiled 'resistor'/wire down in order to fit the chassis back on to the lathe body), so I'll just stick with what I've got.

Very good of you though ...many thanks,
Rob