The Craftmans Shop > New from Old
Puma / Dorman 6LE / MacFarlane B46B / 110 kVA Generator Resurrection
awemawson:
£10 including postage, and yes that’s not a bad idea :thumbup:
awemawson:
Today the plan was to measure the Temperature Sender Characteristic Curve to aid me designing a small circuit to trip at a set upper temperature (Overheat Shutdown)
But first I needed to source some 'Jumper Bars' for my DIN terminals - these things are simply a copper bar with holes at a suitable spacing that when installed parallel up adjacent DIN terminal blocks. I'd ordered some up from RSComponents with the terminal block, and despite being listed as correct for these 8 mm wide 6-10 mm csa cable terminal blocks they were in fact the wrong spacing :bang:
I've had a 'technical query' logged with their help desk since Monday trying to source the correct part, and yesterday they came back with a manufacturers part number but they don't stock them :bang: And nor does anyone else in the UK unless you want to buy 500 off !!! (I only need four 'two hole' lengths!)
OK change of plan for the day - MAKE SOME. No copper strip to hand, but slightly thicker brass should suffice sliced off a bit of chunky angle that was in the scrap box. No great problem, drill a row of holes spaced at 8 mm, slice them of on the band saw, cut them into 'two hole' lengths, clean them up and tin them.
Using the screws and spacer collars from the 'wrong' ones proved the collars to be too long - so all had to be cut down to 8 mm l.o.a. Altogether not a complicated job but very fiddly and time consuming.
. . . got there in the end !
John Rudd:
Shame I wasnt in work, I could have gotten them for you..... :lol:
But, hey ho...,such is life.. :smart:
Looking good as ever Andrew, cant be far off being finished.....? :beer:
awemawson:
So now perhaps I can get on with what I'd planned to do :scratch:
I attached the Temperature sender to a 'Type K' thermo-couple with a hose clip, and wired it to my Comark temperature meter and Fluke V.O.M. on ohms. Firstly I dipped the assembly in a boiling kettle getting 160 ohm and 98.7 degrees Centigrade (It was only later that I noticed that the Comark battery needed changing, but for my purposes this IS OK)
Then I transferred the assembly into a Pyrex flask, poured in the almost boiling water from the kettle, and sat down to plot a 'cooling curve' - this way hopefully the sensor temperature will be a true analogue of it's installed state.
Then I plotted the figures in Excel producing the attached chart.
I've decided to use an LM393 comparator chip and it turns out that eBay abounds with them conveniently mounted on a PCB with a 'set point' twiddle pot. I am going to mount one of these circuits inside a DIN module case along with a miniature relay to give me a closed contact on 'overheat' - the twiddle pot on the PCB will be replaced by another glued in the DIN module case and accessible through a hole for setting.
John Rudd:
Have you considered the case of an open circuit...? Your detector triggers on a rise in temperature wich correlates with a fall in Ohms....
If you have a wire break then it wont trigger?
The relay wont close and no shutdown....
Better to have a function that is failsafe? Ok we're not talking SIL levels here but some protection is better than none?
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