I very much doubt we'll ever be in a position to build our own home, but if we did you can absolutely guarantee that all of this sort of nonsense would be designed specifically to be readily accessible for inspection and maintenance. Likewise the drain cock for the heating circuit would be positioned above a drain so I don't need to mess around with hoses and inevitably spilling manky water at least somewhere. Would also be a proper ball valve rather than those stupid little spigots which flow next to nothing and leak everywhere. Just stupid things which you only need to mess with once every few years, but where a bit of thought at the design stage would make it so much easier.
Latest shipment of bits for the pinball table arrived. In no less than six packages...just WHY do you do this, Amazon? I really miss Maplin for random things like this...I'd normally use CPC or RS for electronic components rather than Amazon, but their postage charges for small orders like this are just horrendous and I didn't have enough other random bits to add to make it up to the free postage limit, so Amazon it is.
The reason I was initially confused and had coils locking on as soon as the 12V bus came up was that I had two types of contactor in place. Look closely at the markings on these.
The one on the right has normally open contacts, and the left normally closed. This was totally irrelevant when I originally put them in here as they were literally just there to make noise and transmit a bit of physical vibration through the frame emulating the moving parts in an actual table. However it became an issue when I decided to use them to switch things!
The things I had hooked them up to switch were a bunch of these.
Generic starter motor solenoids. The reason for this was simply that the little contactors while better than nothing simply weren't violent enough to be convincing. An actual pinball table is a really noisy bit of machinery. A little contactor with a coil that pulls all of about 20mA (about 1/4 of a watt in power terms) just produces too polite and discreet a little "click" for our purposes. These starter solenoids on the other hand pull something like 10A (so 120W or thereabouts) and produce a far more convincing "ka-thunk" which you both hear and feel through the cabinet much more like the real thing. I really didn't want these on the same 12V supply as the PC and interface boards though as big solenoids like these are very electrically noisy - hence using the original contactors initially to provide that isolation (and an additional separate 12V power supply). This presented two problems pretty quickly. Firstly was that four of the coils immediately locked on when I powered the system up - which we have since tracked down to me having a mish mash of normally open/closed contactors. Secondly was that the arcing at the contact points was throwing out so much RFI that it was playing merry hell with the system as a whole and causing the interface board to randomly reset and crash the DOF subsystem.
Time to solve both these issues in one go by upgrading from the mechanical contactors to solid state relays.
I'm surprised I didn't have a few of these kicking around to be honest as they're ridiculously useful. The ability to throw anything from 3-32V at them as the control voltage is a particular bonus from the electronics hobbyist perspective as that has most of the bases covered. Though it is worth noting that they come in DC and AC varieties, and it does matter unlike a mechanical relay/contactor. They also usually want some form of heat sinking if used hard, though here they're being used at only a fraction of their rated power (and at a very low duty cycle) so should be fine without that, especially as the cabinet here is actually pretty cool running with plenty of airflow.
The fact that there are no physical contacts to spark also immediately deletes the arcing and RFI issues we had initially.
The terminal layout is a little different to the original contactors which meant installation took a little longer than it otherwise might have, but it wasn't really that bad. Once we've done a decent amount of play testing I'll go back in and tidy up the new wiring we've added.
I might try to move the middle right one a bit further towards the back as well (or the mid left one forwards) so it's more symmetrical - though honestly you really won't be able to hear the difference from below the playfield.
From a diagnostic standpoint these new relays make my life easier as they have an actual light on them to show when the output is active.
It definitely sounds far better with the new setup - albeit it need of three new solenoids as three of them took exception to being left powered up for about ten minutes when I was initially unaware they were stuck on. Can't say I'm surprised given how hot they got. Only myself to blame there. Just how it goes with projects like this sometimes! At least nothing expensive or hard to obtain was damaged, just a few cheap solenoids which will take less than 15 minutes to change once the new parts arrive.
And good to know Headline are back up and trading again...
