Last couple of weeks have been very busy. Taking an old EM playfield and converting it to modern drivers has been going well. Lots of things have been learned in the process.
1. Don’t use the old wiring. While it looks very convenient and seems to have many of the connections that are needed, it is from the 1960s and the insulation is made of cloth, not plastic. It is a pain to strip the wire which makes it difficult to get a good crimp.
2. The wire doesn’t necessarily run where it needs to run. There is a common ground for almost everything so even more wire could be removed from the bottom of the playfield. If the playfield would have been stripped, and started from scratch, only the needed wires would have been added back.
3. The cheap crimper (KF2510), works incredibly well. It’s been used for 100 mil spaced connectors, standard pinball molex connectors, and spade terminals. It has three different sizes for different connectors. While it isn’t as nice as the $300 molex crimper that only supports one terminal type, it works great for general use. The trick is to start the crimp so that the ratchet holds the connector in its teeth. Slip the wire in to the terminal, and then finish crushing the crimp. The crimps are nice and tight and hold the wires very securely.
After rewiring, this is what the bottom of the playfield looks like so far:
The first picture shows the driver board at the top center of the picture, with an input card on at the bottom of the picture. Second picture shows the entire playfield.
The solenoid driver at the top handles eight solenoids. It includes eight inputs so all the real time aspects of driving the solenoids is local to the little card. The four wire cables on the edge of the is a transmit/receive/power and ground connections. To each solenoid that is controlled by a switch, there is a single wire to ground at the bottom of the solenoid (NFET configuration), and a single wire to indicate the switch is closed. The hot side of the solenoids are all bussed together with the high voltage. The common side of the switches are bussed together with a ground wire. (Each switch connection has a 2 pin header with one of the pins being ground. This gives the flexibility of not needing to run a ground bus.).
The input driver board is very similar except there are 16 inputs per card. Each switch input is a two pin connector which can provide a ground if a common ground wire bus isn’t available on the playfield.
Last big thing that looks out of place is the cheapo power supply. It is a Meanwell LPP-150-48. It only provides 3.25A at 48V. Bought two of them and planned to split the flippers between the two power supplies, but during testing over the last couple of days, it seems like a single power supply might be able to run the flippers. Of course, the second supply is already bought, so it might as well be used. Each of the supplies is $9 on ebay.
Nice to hear the bam, bam of solenoids being driven at 48V. I’m probably going to take a little time to build a second solenoid driver card. (Right now there aren’t enough drivers on a single card to support two of the pop bumpers and one of the kickout holes. Parts are already in house for another two driver cards). Each type of solenoid has been wired up to make sure the driver card configuration is working properly. The flippers have a 48ms initial kick and then a 25% on the PWM for hold. The kickout hole has a 48ms initial kick, no hold, and a dead time configured in case the kick doesn’t clear the ball from the kickout hole. There is a post that goes up and down, which has no initial kick, and only 25% PWM. Last type is the pop bumper which has an initial kick, no PWM, and a small dead time.
The input card is a little more dull at this point. It is currently wired up and shows the status on a computer sitting next to the playfield. Boring. No scoring, no rules, hey it is just a test bench. Enough rules might be written so a game can be played and scoring can be added but no real plans at this point.
Open Pinball Project 