Replacing the dashboard plastic PCB

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Re: Replacing the dashboard plastic PCB

Postby CovKid » 13 Feb 2018, 08:48

or providing you kept the cap that covered the original tungsten bulb, a 3mm blue LED should be fine. Unfortunately blue light travels further (hence its use on emergency vehicles) which is why an increase in resistor value is sometimes the best solution. I actually dipped my LED in black paint which worked ok.
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Re: Replacing the dashboard plastic PCB

Postby CJH » 29 May 2018, 23:49

My winter hobby (DIY Hifi) spilled over into the summer :shock: , and my poor camper has been neglected. But it's given me some experience with designing PCBs and having them made to order. I thought I'd have a go at making a bespoke PCB to replace the dash foil. Based on the excellent schematic from MidLifeCrisis at the start of this thread, and the schematics for the later models provided by ZsZ, I think it should be possible to make a 'one size fits all' PCB that simply needs the wires connecting in the right order, and the correct components soldering to the board.

Here's my first draft. Component side:
Image

LED side:
Image

I've gone for the big 5.08mm terminal blocks because there's space and they're easier to wire up. I've grouped them into 'signals', 'power', 'gauges', 'dashboard lights' and 'buzzer'. The 'signals' connector is a superset of all the different signals that I could see for petrol/diesel/early/late, but I only have an early petrol to actually physically check, so could do with some pointers in case I've missed out any signals. The order of the 'signals' wires doesn't match any specific variant - I just ordered them to make the PCB routing easy. The idea is that the wires on the edge connector would be connected up to the relevant terminals. I may also have a go at making a 'goldfinger' adapter with the same terminal blocks attached, so that the existing edge connector doesn't have to be replaced and the wires can just be run between the goldfinger adapter and this PCB.

I know of at least a couple of corrections that need doing to this draft - the newer schematic provided by ZsZ has an extra diode in the circuit (in the wiring to the buzzer), and a capacitor in the temperature gauge circuit, so I'll add those. And I'm a little unsure of the buzzer wiring, especially the terminal that I've called 'buzz4' because in ZsZ's schematic that wire seems to go to one side of what I think is a missing resistor. From photos I've seen, the PCB foil that connects to the pins on the buzzer PCB seem to use a simple female header, but I could do with knowing what pitch those pins are at, if anyone has one to hand.

A friend at work put me onto a cheap PCB manufacturer in Shenzen, China (and I've since learned that there are many of these) - their turnaround time is incredible and the prices are amazingly cheap. So it's quite feasible to go through several drafts of a PCB in a fairly short period of time without breaking the bank. If these work out, I reckon a bundle with all the components should be really quite cheap.
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Re: Replacing the dashboard plastic PCB

Postby slowcoach » 30 May 2018, 07:19

A kit to solder together at home, cracking idea :-) well done for all your efforts.

I think a key thing would be not interfering with the van side of things, ie the van multiplug. A compatible male plug might be out there somewhere? That would make this thing a real beauty :-):-) I know the whole thing (male and female) can be swapped with any number of available multiplug out there, but would make the project a 'destructive ' one.

I did promise myself though I wouldnt mess with mine again, once I swapped/rewired from an early to late cluster and it miraculously just worked ;-)

Some more pics in here if useful..
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Re: Replacing the dashboard plastic PCB

Postby CJH » 30 May 2018, 07:29

slowcoach wrote:I think a key thing would be not interfering with the van side of things, ie the van multiplug.

I agree - I think the 'goldfinger' PCB/edge connector approach will work. Still looking into how to create that in the PCB design software.

slowcoach wrote:Some more pics in here if useful..
viewtopic.php?t=155394

Thank you - I'll have a read.
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Re: Replacing the dashboard plastic PCB

Postby CJH » 30 May 2018, 08:12

I think I've figured out how to make this 'goldfinger' adapter board. This is what I had in mind:

Image

I need to work on the spacing, width and length of the fingers, and I need to check that the standard (cheap) 1.6mm PCB thickness will work with the existing multiplug, but a simple adapter like this with 14 screw terminals should allow any pin of the multiplug to be connected to any input of the LED PCB.
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Re: Replacing the dashboard plastic PCB

Postby CJH » 30 May 2018, 17:16

I took some measurements from the multiplug in my van, so I think I have the track dimensions/spacing for the goldfinger board correct. I was surprised to find that the multiplug contacts are only present on one side of the plug - the bottom row in this photo - with nothing on the opposite side. Mine's an early petrol dash - are the newer ones like this too? In fact, it would be useful to know if the plug is different in any way on any of the other models, in case the goldfinger board needs to be adapted. Does anyone have one to hand that they could compare with my photo?

Image

Here's what I think the goldfinger adapter board might look like, with the correct dimensions. The good news is that a standard 1.6mm PCB should work well, which will keep the price down. Despite the multiplug only having terminals on one side, I'll probably have the contact fingers etched on both sides of the board since it doesn't cost anything extra - that way the board can be flipped over (and the wires swapped) in the unlikely event that the fingers on one side get damaged.

Image
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Re: Replacing the dashboard plastic PCB

Postby slowcoach » 30 May 2018, 17:54

I think the early and late multi plug are the same. In The thread of mine i linked to above, I swap an early cluster with vertical plug to a late cluster with horizontal plug and remove order the pins inside the multiplug. It was a perfect push fit onto the late cluster.

Your goldfinger concept looks very like the clustermaster solution. I remember reading maybe on samba that someone had to make the contact board thicker (as you mention) with electrical tape layered up, so the contacts were snug on the pins
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Re: Replacing the dashboard plastic PCB

Postby CJH » 30 May 2018, 18:09

slowcoach wrote:I think the early and late multi plug are the same. In The thread of mine i linked to above, I swap an early cluster with vertical plug to a late cluster with horizontal plug and remove order the pins inside the multiplug. It was a perfect push fit onto the late cluster.


Thank you - good to know.

slowcoach wrote:Your goldfinger concept looks very like the clustermaster solution. I remember reading maybe on samba that someone had to make the contact board thicker (as you mention) with electrical tape layered up, so the contacts were snug on the pins


That's interesting - I wonder if the Clustermaster edge connector uses a thinner PCB. I tried a small piece of 1.6mm PCB and it was quite a tight fit. The jaws inside the plastic multiplug moulding limit what will fit in there, but I'm not sure if it was a tight fit because of those jaws, or because my spring terminals are still reasonably springy. I'll have to get out there again for a closer look to make sure.
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Re: Replacing the dashboard plastic PCB

Postby CJH » 30 May 2018, 18:34

I went out for another look. I think the issue is not whether the spring terminals would make a good contact with a 1.6mm board (I'm certain they would), but whether the mechanical grip from 14 of them would be enough to hold the PCB in place inside the connector. My small piece of 1.6mm PCB seemed quite firm, but it's not weighed down with 14 wires, or being shaken about on the road.

The only thicker board that this Shenzen factory offer is 2mm, and it's much more expensive. I think it would still fit, and if it's necessary to make a better fit then we're still not talking big sums for each board. But I think I'll go for 1.6mm for the first prototype to see how it goes. I'll make sure it's a tight fit lengthwise. I might even add an extra 'tag', at the #1 pin end, to fit into the slot on the outside of the multiplug housing - I think that would make it less likely to twist out of the housing.
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Re: Replacing the dashboard plastic PCB

Postby CJH » 30 May 2018, 18:51

Something like this maybe. I added a tag at the #14 pin end as well - different spacing because of the asymmetric moulding. I think I could make the resulting slots very slightly too narrow, so that they grip nice and tight.

Image
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Re: Replacing the dashboard plastic PCB

Postby CJH » 30 May 2018, 19:04

...and some holes for a zip tie.

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Re: Replacing the dashboard plastic PCB

Postby AngeloEvs » 30 May 2018, 19:30

I designed mine about 10 years ago and that is how I did mine, the other solution was to use double sided PCB but that is very wasteful. The PCB edge connector is a separate board and is pinned through and soldered. Standard PCB thickness is fine but, to give added secure fitment and to prevent any possibility of attempting to fit connection block to the PCB the wrong way around (as is the original VW design), either side of the edge conx is slotted. These slots have to be different widths to suit the VW multi connector which has different thickness tangs either side of the connector itself.

I designed mine mainly to develop a custom dash with Tacho but also fitted about half a dozen for other Owners to replace their faulty membrane types, there was nothing else on the market at that time. I remove and utilise the original VW LED, DOPs and Regulator sockets and, as you can see, I use separate PCBs with connector plugs for the Main board, LED board and DOPs board. Mine has been in service for over 10 years now so well worth doing, I have one spare made up and fitted to a Dash which will be offered for sale on Club 80-90 or EBAY.

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Re: Replacing the dashboard plastic PCB

Postby CJH » 30 May 2018, 20:18

Very nice. Home etched circuit board? That's quite an undertaking. I made a single-sided circuit board some years ago (for a 240VAC to 5VDC linear supply) by drawing the tracks manually in Powerpoint and then using a printout onto a transparency as a mask. I chickened out of doing the etching at home though - had the lab at work include my job in one of their etching sessions.

Things have come on enormously since then (or perhaps they had already, and I just didn't know where to look). I can now design the schematic in one window of the software, layout the components and traces in another, then upload my files to the Chinese fabricator and get back 10 professionally-made PCBs ready to solder in a week or less. I've paid more in duty and DHL shipping than I have for the PCBs themselves. UK fabricators still seem to want to charge 10-50 times the price of these Chinese fabricators, and if you want them turned around in as little as a week then double it again (or more).

AngeloEvs wrote:... to give added secure fitment and to prevent any possibility of attempting to fit connection block to the PCB the wrong way around (as is the original VW design), either side of the edge conx is slotted. These slots have to be different widths to suit the VW multi connector which has different thickness tangs either side of the connector itself.


That's where I've ended up. It means there's no point in having the fingers etched onto the opposite side of the board - single-sided is all the connector needs.
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Re: Replacing the dashboard plastic PCB

Postby AngeloEvs » 30 May 2018, 20:57

At the time I used the PCB making equipment at work and I also have my own, getting them made is the better option if you are marketing as a diy kit, making your own is too labour intensive and not cost effective. Sent you a pm regards getting PCB's made in China.
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Re: Replacing the dashboard plastic PCB

Postby CJH » 31 May 2018, 07:24

AngeloEvs wrote:Image8090b by Angelo Evans, on Flickr


Hi Angelo

Is the circular item in the lower centre of your dash (centre-right of your photo) something that you've added? Or is it perhaps the standard-fit LCD clock that many dashes have? I ask because my current draft of the LED PCB uses the space below the LED panel for the connection terminals (see below) - if that circular item is standard it may foul the lower part of my board so I might have to think again.

Current draft. Minor changes since last time: 'IGN' plane added to LED side, so that I don't have to manually route all the ignition connections (already had a GND plane on the component side), resistors aligned slightly better. Still to do: add that capacitor and the extra diode, increase the distance between the resistor pads to allow more flexibility in resistor choice. I need to check all the values, but I think most will be fine with 0.5W, but sometimes it's nice to be able to fit bigger resistors depending on what's available.

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