Golborne Vintage Radio

Well, that's what they always say in the BMD Section

Back when David ran this ESR Meter Thread on the other Forum I thought 'I'll make one of those'. Around the same time someone Posted a link to a Capacitance Meter kit - http://www.technobotsonline.com/capacita...32208.html - and I thought I'd better have one of those as well. Next I considered what to do about enclosures - either two the same or a larger one containing both meters. I'm not quite sure how it happened but David kindly made me one of his splendid boxes, plus a front plate and a PCB, which even included the critical components. I've reported on the construction of the ESR Meter in David's Thread. So, what about the Capacitance Meter? After some pondering I threw myself on David's mercy and asked him to make me another box, which of course he did. One of these days I'll make a Comb Jig, honest.

So, to battle. Step one was to gather the necessary components. Next, assemble the PCB. The data is quite reasonable, and it's all duplicated on the Manufacturers Website just as a check. One slightly tricky thing to beware of is the 5 band resistors, some of which are not very clear, so a meter is handy. I also added a socket for the processor and some sleeving on the Display legs. Somewhere along the way I lost one of the electrolytics, but as it's only supply decoupling I fitted one that I had - more about that later. I didn't bother fitting the various sockets and switches as I was going to duplicate these with front panel versions. Connecting it to 6 AAAs proved it worked so the next step was to cut a rectangular hole in the panel - David's PCB offcuts are pretty strong and I finished up chain drilling and filing - and drill holes for the switches and terminals. Again, not wishing to have too many holes in the front panel I mounted the PCB on four spacers which I glued on. This is where the replacement electrolytic came round and bit me - it was too tall. Ah well, mount it on the back, but see later. Next I wired the switches and battery, and connected the terminals using BTC and sleeving. I also connected the front panel (copper) to the Negative Test terminal as advised by the instructions. The last step was to screw it into the box, make and fit some labels and tidy up. That's when I found the 'missing' electrolytic!

It gives every impression of working splendidly, although I haven't checked it against a couple of my bridges yet. Anyway, I didn't want it as a precision instrument, just for a quick check on values. I think it will be a useful addition to the bench, along with the ESR Meter.

Alan

[attachment=4205][attachment=4206][attachment=4207][attachment=4208][attachment=4209][attachment=4210][attachment=4211]

That looks very respectable Alan, well done, puts my rats nests efforts to shame.

Lawrence.

Lawence,
Thanks for the encouragement but it is a Commercial Kit and a David box. You can't go far wrong with that as a starting point.
I think they look quite neat though.
Alan

Glad to see that you've finished the kit Alan, and that the box was 'fit for purpose'!

The kit is so cheap that I couldn't resist buying one on impulse, even though I have a couple of cap meters already. As it comes, it's obviously meant to be used un-boxed as a 'bare bones' project, but like you, I'm planning to put mine in a box to match my other bits of home-brew test gear. I'd thought that the digits might look a bit odd without a red filter in front of the 'window'. Polarised red filter plastic used to be widely available, but I've drawn a blank on that, and yours looks fine as it is so I'll probably do likewise. Handy to have a zero button to cancel out the stray capacitance of test leads. Initially, I thought that the little row of test sockets on the PCB were for separate ranges, but on looking at the circuit, I realised that the sockets are 'commoned' for each leg - they're just spaced so as to plug in caps with different lead widths, and the meter is in fact auto-ranging. Hence, as you've done, all that is needed is a couple of test points on the front panel.

What's not to like, at under £15 inc P&P?

Low consumption too, despite the 7-seg LED displays, and as it's only used for a few moments at a time, battery consumption isn't an issue.

Neat eh?

David,
Yes, the digits show up quite well. I was pretty sure that I'd read somewhere that they were a bit faint and lower drive resistors were needed. However, I couldn't find it again so I just used what was in the kit. The picture was taken with flash at an angle. I expect in bright sunlight they might be a bit 'difficult' but I reckon I can put up with that.
And once again thanks for the box and panel.
Alan

Thanks for your further comments Alan.

I first learned of this kit back in 2010 from a UK amatuer (M0WYM) who'd built the kit and was pleased with it. He said that the instructions were sprase, so he helpfully wrote some notes to help others who might wish to build the kit. His notes can be found here: http://www.radiowymsey.org/capmeter.htm

The kit is fairly simple to construct on a high quality plated-through hole screen printed PCB to aid component placement, but does need a box in which to house it. It has an accuaracy of 0.1% on the lower range, and if caps have high leakage, will - as with most cap meters, show a high reading, which helps identify suspect caps.

It covers from 1pF to 500uF in automatically selected ranges and can be powered from either a 'wall wart' from 8 - 16V DC, or a battery. As the consumption is less than 30mA, a 9V battery should last for quite a long time, given that the meter is used only momentarily to test a cap. As I said earlier, it can be zeroed, so any stray capacitance can be nulled out before testing low value caps.

Although Sparkfun, who market the kit, are based in Boulder Colorado, they do have European distributors and I got my kit from:

http://proto-pic.co.uk/capacitance-meter-diy-kit/

Hope that might be of interest to anyone who may wish to build this useful little project, which at the time of writing costs £11.02 inc VAT + P&P - about £15.00 all together.

(03-03-2012, 10:48 PM)Yorkie Wrote: [ -> ]Polarised red filter plastic used to be widely available, but I've drawn a blank on that

Farnell still sell it, but it's not cheap - 177-147 is £9.74 for a 105 by 35mm sheet.

They also sell bezels, complete with a filter, for around half the price - have a look at 175-705 for example. The sizes available are 20.6 by 34.9mm, 20.6 by 50.8mm and 20.6 by 76.2mm. I've quoted window size there...

I'm sure I have some of this stuff somewhere - probably taken from old kit - so if I ever find it, I'll be in touch.

Mark

I've got a DPM wich came with a Bezel which is fitted with a red filter. I tried it with the Cap. Meter display and in all honesty it's hardly worth it.
Alan

(06-03-2012, 01:54 PM)Mark Hennessy Wrote: [ -> ]

(03-03-2012, 10:48 PM)Yorkie Wrote: [ -> ]Polarised red filter plastic used to be widely available, but I've drawn a blank on that

Farnell still sell it, but it's not cheap - 177-147 is £9.74 for a 105 by 35mm sheet.

They also sell bezels, complete with a filter, for around half the price - have a look at 175-705 for example. The sizes available are 20.6 by 34.9mm, 20.6 by 50.8mm and 20.6 by 76.2mm. I've quoted window size there...

I'm sure I have some of this stuff somewhere - probably taken from old kit - so if I ever find it, I'll be in touch.

Mark

Thanks for reading and looking into this Mark, and for your helpful reply.

I think I'll give it a wide berth at that price - it's as much as the kit cost. At least Dick Turpin wore a mask

(06-03-2012, 02:41 PM)AlanBeckett Wrote: [ -> ]I've got a DPM wich came with a Bezel which is fitted with a red filter. I tried it with the Cap. Meter display and in all honesty it's hardly worth it.
Alan

Your's looks fine without a red filter Alan, and the LEDs are all moulded into one unit encased in what looks like black resin, so don't look too bad. I must get on and make mine - I've got three projects on the go right now - that cap meter, a 11 MOhm input analogue mV/Voltmeter, and a 10V precision voltage reference. I'm completely indisciplined and unfocused on time mangement easily distracted. I really ought to finish one thing before I start another, but realistically, it's never going to happen. It's a cross I have to bear and it drives my wife nuts. She still sees me as 'work in progress' and I don't think the awful truth has yet dawned on her that I'm quite beyond redemption.