285 replies to this topic

[mjr]

I found the following circuit on the Internet. Do you think it would work to monitor the state of the output? I would probably change the 40K to 10K and leave your 47R instead of using 100R. At 12V the 1K resistor would have about 10 mA on the LED.

 

That looks like it should work, although I'd test it before committing it to a PCB to be sure.  I think I'd try simplifying it by moving the LED to the high side of the opto (i.e., between the opto collector and +12V) - that would let you dump the 40K, since you don't have that split path to ground on the low side any more with that.  One less part to pack into the limited space, if it works.

[MikePinball]

I'm trying to find substitutes for some of the parts that are more readily available and not obsoleted. Yes I know I can buy the parts from China (sometimes the USA too but I'm sure they got them from China and are simply reselling).

 

What do you think of the following:

• LTV-846 or perhaps the PS2501-4 for PC847 opto-isolater
• RCX300N20 for the BUK7575-55A MOSFET

The TLC5940 is more of a problem. The HTSSOP-28 version would work for me but I can why people want sockets and may have difficulty with this SMD part. A breakout board is going to be difficult too as the pinout is different and the board is 600mil instead of 300.

 

Mike

Edited by MikePinball, 03 November 2018 - 11:07 PM.

[MikePinball]

On further investigation I am going to go with:

• LTV-847 4 channel opto-isolator (not pin compatible but I like the pinout better) - Mouser $0.81 each
• FQP13N06L MOSFET (recommended by mjr elsewhere) - Mouser $0.99 each

Mike

[MikePinball]

I have done some more work on the output board so let me know what you think and if you see any problems.

 

I made the following (substantial) changes to the originals from MJR:

1. Added 20mm x 5mm fuse holders. Wire links can be inserted for outputs where fuses are not required.
2. Added LEDs for each channel to indicate when a channel is on.
3. Added LEDS to indicate power available for both 5V/3.3V logic and 12V/24V power outputs.
4. Fuses and LEDs necessitated reducing number of outputs from 32 to 16. Many people only need 16 at most. Additional boards can be used to get more outputs.
5. Added 3.81mm (0.15") pluggable terminal blocks for high current outputs (bigger and can be unplugged easily)
6. Added 16-way header to take direct outputs from KL25Z board rather than using TLC5940 serialized I/O.
7. Renamed N$68 trace to 3.3V
8. Manual routing with only 45/90 degree traces and minimal number of vias using 16mil or larger traces

Here is a picture from Eagle3D. You can find the full Eagle files and pictures in this file: ps2-MikePinball 20191120.zip.

 

Mike

 

Edited by MikePinball, 22 November 2018 - 02:29 AM.

[MikePinball]

I have a question on the Pinscape design that should help me with what I'm doing.

 

Normally you need a resistor on the input of an opto-isolator to reduce the current flowing through the LED. The PinScape boards have none. Is this because the current is constant current from the TLC5940 and is roughly 8mA (using the 4.02K resistor)?

 

What happens if I connect an output from the KL25Z directly to the opto-isolator? I'm thinking that even though the current is limited from the KL25Z, I need a resistor. Assuming 3.3V output and 1.2V forward voltage, then for 8mA, I would need a 263R resistor. Rounding this up, a 270R would do. Does this sound right?

 

Mike Pinball

[mjr]

Normally you need a resistor on the input of an opto-isolator to reduce the current flowing through the LED. The PinScape boards have none. Is this because the current is constant current from the TLC5940 and is roughly 8mA (using the 4.02K resistor)?

 

Right (it's actually more like 10mA - the formula per the data sheet is 39.06/R).

 

 

What happens if I connect an output from the KL25Z directly to the opto-isolator? I'm thinking that even though the current is limited from the KL25Z ...

 

Actually, there isn't any regulation for the KL25Z GPIOs.  They're "limited" in the sense that you can't draw more than the limit without frying the whole CPU, but they're not "limited" in the sense that there's some kind of current regulator that will prevent that...

 

 

... I need a resistor. Assuming 3.3V output and 1.2V forward voltage, then for 8mA, I would need a 263R resistor. Rounding this up, a 270R would do. Does this sound right?

 

So yes, you absolutely need a resistor.

 

The "absolute maximum" in the data sheet for GPIO pin current (source or sink) is 4mA per pin for most of the GPIO outputs.  (A few are specially designated for a higher limit.)  

 

As usual with these things, there's also a separate limit on the combined current you can safely draw from all GPIOs in aggregate, and that comes to about 1mA per pin if you happen to have them all on at once.  It's not likely that they'll all be on at the same time, but it's not impossible either, so I like to be conservative and try to keep them to about 2mA whenever possible.

 

So plugging Vs=3.3V, Vf=1.2V, and If=2mA into an LED calculator, I get 1.2K.  If you're using this to drive an opto, that's definitely on the low side (the optos data sheets always base everything on If=20mA), but in practice the 817/847 types trigger fine with it.  It might not be enough for satisfactory brightness if you're trying to drive an indicator LED, though - for that you might want to add an NPN stage so that you can drive the LED at more like 20mA.  If you use any common small signal NPN (2N4401 is cheap and easy to find), you get up order of 100mA with 1mA or less on the base.

[MikePinball]

Thank you for the help. The LED is on the emitter of opto-isolator transistor and that works fine when the opto is fired.

 

According to the datasheet, the minimum current for the opto-isolator LED is 2.5mA. 1 or 2mA might not quite be enough. I tested with 1K resistors (2.1mA) and it worked fine.

 

Right now I am going to have a maximum of 12 outputs (10 contactors + two LEDs) so the maximum output current of 100mA should be enough for 12 outputs especially as it is very unlikely all will fire at once. I assume 2 LEDs, 2 flippers and one other contactor is probably the most likely worst case which is only 10.5mA. Even all 16 outputs firing at once is only 33.6 mA.

 

Mike Pinball.

 

Updates on 12/28/18 in red.

Edited by MikePinball, 29 December 2018 - 05:54 AM.

[toy4x4]

MJR,

 

Do you still have a set of boards available? 

 

 

 

I was wondering if anyone has an expansion PC Board (populated or not). 

 

I just refreshed my supply, so I have all three boards (main, power, chime) available.  Unpopulated, I'm afraid.  PM me and let me know what you need.

 

 

Last, I am creating a 3D printed part that will hold the sliding potentiometer which I got from Jameco Electronics.  To give back to the community I will upload the STL files so others can print their own.  

 

That's great!  I'd be happy to include a link or host a copy on my site if you'd like.

 

[mjr]

Do you still have a set of boards available? 

 

Yes, I have main boards and power boards on hand.  (I'm out of chime boards at the moment - I need to reorder a batch of those at some point.)  If you want a set, PM me so we can arrange details.

[MikePinball]

It might not be enough for satisfactory brightness if you're trying to drive an indicator LED, though - for that you might want to add an NPN stage so that you can drive the LED at more like 20mA.  If you use any common small signal NPN (2N4401 is cheap and easy to find), you get up order of 100mA with 1mA or less on the base.

 

I ended up using two ULN2803A Darlington transistor arrays. See the reply at this link for more details.

[PinballEngineer]

Apparently you have boards available as of Jan 4? Still have any available? I'm very interested. I tried to send you a pm, but it said you couldn't receive any more private messages (probably because I'm a new member).

 

Thanks for the guide BTW. It's amazing! I wasn't sure if I wanted to build one when I started researching virtual pinball machines, but after I started reading your guide I am totally jazzed about the project!

[mjr]

Apparently you have boards available as of Jan 4? Still have any available? I'm very interested. I tried to send you a pm, but it said you couldn't receive any more private messages (probably because I'm a new member).

 

Sorry about the PM limits - it's not you, it's just because my mailbox is full.  I've been keeping boards on hand and I'd be happy to send you some, as long as you're in the US.  You can reach me by regular email at mjr underscore at hotmail dot com.

[nevess]

What is the best to get fully assembled boards in Europe?

[mjr]

If you do a Web search for "pinscape boards germany", you can find the one seller I know of in the top results there.  (I believe he's had some conflicts with people on the forums here, so the forum software here might not let me post a direct link.)

[nevess]

If you do a Web search for "pinscape boards germany", you can find the one seller I know of in the top results there.  (I believe he's had some conflicts with people on the forums here, so the forum software here might not let me post a direct link.)

Thanks, I will check it out.

[MaMikee]

Are these PCBs still available?  I'd like to get a couple controller boards to mount my Freescale mBed on.

 

Thanks

[Pariah Zero]

At the risk of being a forum healer with really bad timing (ie. a necromancer reviving dead threads):  Are PCB's still available?

[mrarcade]

be aware the tlc5940nt is no longer available. you can read about my multiple attempts to buy them as well as the conversion board solution in this thread:

https://www.vpforums...c=34102&page=49

[MikePinball]

If you do a Web search for "pinscape boards germany", you can find the one seller I know of in the top results there.  (I believe he's had some conflicts with people on the forums here, so the forum software here might not let me post a direct link.)

I am surprised that you would recommend a known and repeated scammer in Germany. You can be lucky to ever receive hardware from him, and it often doesn't work. I still get people telling me that the bought from him and have non-working hardware. They want to buy my Pinball boards but unfortunately I am not currently making them.

 

As a consequence I recommend another maker who has a GOOD reputation. His shop is here: https://shop.arnoz.c...rig-master.html. The rigmaster board is supported by the Pinscape configtool.

[MikePinball]

Here is my SMD version of the TLC5940 using the VQFN32 version of the chip. This is harder to solder by hand but has the advantage that it doesn't cover up any holes for the connector pins into an IC socket. If the TLC5940 continues to have problems then I might make up a batch of these for people to use.