Mike's Project Tracker

Multimeters can give false voltage readings if they have a low battery even without the low battery warning. I mounted the components for the voltage regulator for the MOSFET Driver Board in order to test the regulator by itself.  The regulator drops the voltage from the 48V solenoid power supply to between 1.2V to 30V.  The 30V upper limit was set because the D223 optocouplers cannot handle more than 30V so it is pretty important that this works. MOSFET Driver Board with Linear Regulator Mounted The regulator pot was used to set the voltage output to 12V but the 12V started to drift high, just tenths of a volt at a time.  I thought that my regulator just needed to come to steady state as my set resistors were heating up and thereby causing the voltage to drift.  Also, the 48V power supply is one of those cheap ones off eBay or Amazon so I did not trust it very much.  After a few minutes, the voltage was still going up and I tested the voltage supply ...

Red PCBs do look sharp.  The MOSFET Driver Board PCBs came in and overall they turned out well.  Compared to previous boards I have ordered from Seeedstudio, the tin on the pads is a bit uneven and the inkjet for the silkscreen must have got gummed up.  You can see that the silkscreen is a bit messed on the white rectangle I left as a space to write on.  Small gripes for hobby PCBs and overall I'm quite happy how they turned out. MOSFET Driver Board PCB

Final version?  I hope so.  I have gone back and redesigned my solenoid driver board several times.  In previous versions I attempted to offload some of the logic from the microcontroller.  For example, I used a Schmitt-Trigger [74HC14] with an RC network to provide a single pulse to the solenoid.  Also, I added in a PWM signal to set the average voltage 'seen' by the solenoid.  This worked but was very limiting to have the pulse length hardwired in and it was difficult to adjust without more expensive precision potentiometers. I chose to simplify my circuit to make it a general MOSFET driver for flexibility.  Since I have more than enough space inside my pinball cabinet, it was not a problem to have the extra boards.  The boards were designed to have 4-channels since by default I would get a minimum of 10 boards for the same price from Seedstudio.  Also, the cheapest board option was restricted to 10cm x 10cm otherwise the price balloons ...

Last November, I fried my 'lab power supply' that I made from a computer PSU.  I was testing my solenoids and the stress was just too much for the PSU.  The mistake I made was rapidly turning on and off my solenoid which likely resulted in voltage transients (spikes).  Since the PSU does have a current limiter, it was likely the constant voltage spikes that caused the damage.  There are various methods to suppress voltage transients such as by-pass capacitors and zener diodes.  In particular solenoids and other inductive loads experience these voltage spikes, hence my no longer functioning bench power supply. ATX Breakout Board I could have just rebuilt the same power supply by adding binding posts etc to the PSU housing but after searching the internet an ATX power supply breakout board seemed a popular option.  The main advantage compared to my old power supply was the addition of fuses on the outputs.  The extra safety this provides is perf...

Managed to get it down to three vias and the routing is a bit better.

Here is an image of my solenoid driver board.  It is 99% autorouted but I did make the traces for the positive inputs for the solenoids much larger for the 10 amps peak they might see.  The current is very brief so the traces are probably larger than they need to be.  The traces for the solenoid inputs are 100 mils, the rest at 16 mils and I have the entire top and bottoms of the board as ground.  There are five vias but I do not think I can avoid them.  I also probably need to line the ICs in a way that is more pleasing to the eye and I have to add the silk screen layer to label everything.

Here is my schematic so far for my solenoid driver board.  The PWM control took up too much space to include on the board due to the limitations of EagleCad's freeware.  Each control circuit has two inputs, one for the trigger and one for the PWM power control.  I might add in a way to disable the single pulse generator so that you can just trigger it on or off if there is room on the board.  However, I can only think of a few instances that would require it as most solenoids will burn out if left on too long.  I will post the EagleCad files including the board layout when I am finished.

Now that I have been lazy about working on my pinball machine for a while, I got mad enough to motivate myself to work on it.  The solenoid driver board is being re-hashed, again but in the meantime I am trying to put together a 6-channel audio mixer and stereo amp. Just quickly, to update on the solenoid driver board I've been working on the schematics for it.  I am at least doing a better job of documenting my work.  I will be posting the schematics and my first board layout soon.  Due to the board sized limitation on EagleCad freeware , I can only fit (at least I think I can) the circuitry to drive six solenoids.  I am fine by this.  It makes my solenoid power distribution more modular.  I will likely use three boards for 18 solenoids.  The EagleCad freeware is limited to a board size of 8 x 10 cm.  I could have used KiCad as it is unlimited but from what I have heard it is not as user friendly and everyone has EagleCad which makes shar...

I purchased a little while ago the worst pinball machine playfield ever: Williams' Hardbody .  It is considered to be one of the worst pinball machines ever made and that's why it was cheap!  I'm scavenging usable parts from it.  Drop targets, raised ramps, ball savers, you get a little bit of everything from the playfield.  I also got Laser Ball , an average pinball playfield. Bally HardBody Williams Laser Ball  This is by far and away the cheapest way to get parts.  I paid $200 for both playfields and considering that even used pop bumpers can cost $30 so it was well worth it.  I'll likely have a ton of parts left over from my project in the future but if anyone wants to buy an unpopulated playfield let me know. The Laser Ball playfield is actually in good condition but is just rather dirty from being stored for so long.  I've also kept the non-broken plastics. 

In my initial solenoid power board design, I used a PWM signal to control the power to the solenoids.  I used an AND gate so that the PWM signal could be constantly running but require the microcontroller's command to turn on.  This is done by putting the other pin on the AND gate to HIGH.  I have added a PWM component to the single pulse generator so that I am able to control the average voltage of the pulse. I am also trying to offload as much work as possible off the microcontroller so that it runs quickly.  For most of the solenoids in the pinball machine, the power that is required will not change during the game.  The only ones that I can think would possible change would be the pop bumpers.  I would like them to be stronger during certain periods of play.  To do this, I think I will need to use a 50V power supply in order to be able to play the game at a lower power level and then to have enough reserve to raise it to a noticeable difference....

While testing out my new test playfield with just the mechanical switches, one of pop bumpers got stuck.  As the pop bumper was stuck, the switch remained closed, and this kept the solenoid powered.  The switch generated a lot of heat melting the pendulum from the pop bumper skirt until it melted.  As it melted it became short enough it could not trigger the switch anymore and finally released.  This is not good.  This is a bit of a safety issue.  What happens when you are playing the game and you do not notice. To solve this problem, I determined I needed a single pulse that would not fire again until the switch had been pressed again.  So even if the switch is held down, the pulse is sent only once.  The lower logic level voltage (5V) will not heat up the switch as it will be current limited by a resistor rather than just the solenoid on 35V. To produce this single pulse I used the following: 74AC08 - AND Gate 74HC14 - Hex Inverting Schm...

All the playfield machinery I have I purchased used online or from online classifieds.  Some components are direly expensive such as the ball trough.  So I decided to try and make one. Makeshift Ball Trough / Ugliest Sheet Metal Work Ever Above is a photo of the ball trough I made.  It is ugly, poor workmanship on the sheet metal and the ball launcher is a little loose; but it works.  I purchased a very cheap sheet metal hand brake to make this and other brackets.  I also made a slingshot mechanism as well. Makeshift Slingshot Mechanism It works.  The only issue with the slingshot mechanism is that I had to thread some 1/4 inch rod.  I used two nuts to lock the far side so that it does loosen during use.  The two nuts take up a lot of space a leave little room for the two microswitches that will detect when a pinball has hit the slingshot.  These are a real pain to make when, honestly, I do not have the right tools for it. ...

What we have here is playfield built wrong.  It is not because it lacks parts, or does not have all the features you want it to have.  It is wrong because it is too thick!  My research has led me astray.  I used your standard 3/4 inch plywood to build the cabinet including my prototype / test playfield.  After I put those pop bumpers on and they did not work consistently, I investigated. Bad Playfield!  The playfield is too thick for pinball components. The pop bumpers under the playfield. The photo above shows the three pop bumpers under the playfield.  The pop bumper is triggered when the pinball hits the pop bumper skirt.  The skirt has a pendulum that sticks down below the playfield and can be moved from its centre resting point to a point on the circumfrence of a circle.  The circle's size depends on the angle that the pendulum is actuated to.  There is a leaf switch with a saucer.  Then the pendulum swings out, t...

I also have some more new toys. I was frustrated with my old El Cheapo soldering iron. The tip was too large, the temperature was not regulated and the tip would just disintergrate through normal use. So I bought a nice 60W American Hakko soldering station. My American Hakko 936 60W Soldering Iron What a world of difference. When buying a soldering iron look for ones with ceramic heaters and that have interchangable tips that have the heater inserted. The difference between spending $30 bucks on a soldering iron to one for $70 (Like this one was, on sale) is well worth the price jump.  If you are even thinking of building electronics, do not both with the cheap ones.  Its just not worth it, buy something like this life saver of a soldering station! Makita Li-Ion Drill / Driver  Another tool that I purchased is a lifesaver as well but it is not a necessity like the soldering station.  I purchased a Makita 18V Li-Ion drill.  It was my birth...

I was getting to the point where I really needed to build on something. I have numerous pinball parts but have nothing to attach them to. I managed to find some pinball plans for a Williams Widebody pinball machine. All the measurements are in mm sadly even though all pinball cabinets are in inches. I converted and change it all to the nearest quarter inch. Well sort of. The guy who measured this was intending on using 45 deg cuts in the corners. My skill saw is too cheap for that so I changed the measurements for butted joints. The interior is set for a 23.5" wide playfield. The length of the cabinet is 51.5" in total. I used 3/4 inch plywood so the bottom would be 50" long for example. You can pretty much dimension the rest from there.  I did get a little chipping of the plywood but I went out and bought a blade with more teeth for finer cuts. It's a 60 tooth saw blade and my skill saw doesn't really have enough power for it so I have...

If you are sick of them at this point, you know how I feel.  I was missing a switch.  That's just shocking.  The only way to turn it off was to unplug it. I had no indicator lights as well.  Guess I was not thinking much about safety when I built it.  Another problem with my power supply was I was using old oil and paper capacitors. They work and I still have them but they take up a lot of space, are not as reliable, and on the whole, my power supply was rather ugly. The new sexy version of my solenoid power supply! Out with the old and in with the new. This is my rebuilt power supply. I grabbed a scrap piece of aluminium from work and got a 90 deg angle put in it. The aluminium will act as a heatsink and also minimize electromagnetic waves emitted by the power supply though this is small because I'm using a toroidal transformer when compared to a conventional transformer. I plan on using some chicken wire I happen to have to make a farada...

My extra room in my condo was getting a little overrun with electronic components. It was time to build a proper workbench instead of littering my computer desk with all sorts of junk. Also, it was an excuse to buy some new tools such as a skill saw. Cheaped out on the skill saw and got a $60 7 1/4 inch saw. Ah, it works. I did purchase a plywood blade, ie. many teeth, to make smooth cuts through plywood.  It made a huge difference compared to the rip blade that came with the saw.  I also have a mastercraft jigsaw I purchased on sale at Canadian Tire for $45 bucks. That's for later though when I need to make odd cuts for the playfield. My workbench covered with... stuff. My trusty new skill saw. Here is my workbench. Evidently I've been using it. I made it myself using 3 2x10's for the top and 2x4's for supports. I used drywall screws because they work and are cheap.  Drywall screws are more brittle than wood screws but for most stuff they...

Now I've shifted my focus to building a I/O board for all the many lights and small devices used on a pinball machine.  In order to reduce the amount of space I would need I opted for Darlington Arrays which are many darlington pairs (remember those?) in a nice DIP package. I am using ULN2003 darlington arrays.  They have 7 outputs and I wished they had 8 outputs then it would line up so nicely with my shift registers.  Unfourtunately, they do not and my arrays and shift registers are staggered.  Initial Testing of the I/O Board controlling some LEDs via a IDE cable from a computer. The I/O board uses shift registers to control all the outputs and darlington arrays to sink the current.  It is important to note that they sink the current and do not drive them.  The 'outputs' of the array are hooked up to the LED which is then hooked up to the positive voltage.  The darlington pairs inside the chip, when turned 'on', allow current to flow t...

Pinball solenoids come with designations like 23-800.  The first number, 23 in this case, represents the American Wire Gauge (AWG) used.  The second number, and the more important number, is the number of windings which is related to its power rating.  A solenoid with less windings, say 400, is more power and is used for such applications as actuating the flippers.  These solenoids get very hot very quickly, which increases the resistance of the solenoid thereby decreasing the current and therefore the power.  To avoid overheating, these high powered solenoids will have two coils.  One for the main actuation of the solenoid, and another to maintain the position.  The second solenoid will have a smaller wire gauge and more windings.  In example, my flipper 'coils' are 15-411, 15 AWG and 411 windings.  They are quite strong and found in some of the latter Williams pinball machines such as the popular Adams Family machine.   You...

This entire time I've been using the PC power supply just by sticking wires in the ATX plug. Not a great solution as the wires have a habit of popping out. To turn on an ATX type power supply you need to short the green and ground (black) wires. ATX powers supplies are the most common type. The only other one I know of are Dell's, which have a special configuration for the 'ATX' plug. Same style of connector, completely different voltages at each pin. This is why your nice new motherboard explodes because you used your old Dell power supply when building a new computer. My friend knows this from personal experience. Lab Power Supply Formerly of PC I have managed to take that old PC power supply and make a proper lab power supply out of it. It's a rather simple setup. You can find out how to do this yourself on http://www.instructables.com/id/ATX--%3E-Lab-Bench-Power-Supply-Conversion/step2/Planning/ and you can find all sorts of other odd do...