Updated: Build Files For 2-3 Aspect Signal Actuator; Common Anode LEDs; Video Added

Just adding the Excel BOM files for these boards, both domestic and offshore versions.

Total costs are about $15 for domestic and $5 for offshore. About the usual difference. One huge difference is $6.10 each for OSH Park boards, versus less than a dollar for offshore. I have also included .1" pitch screw terminals for both, though these are not available domestically from what I can see. You can reduce the price by about one dollar  a board by eliminating these and going with a lesser expensive option such as DuPont connectors. Another option is to simply solder wires to the board connections. There are lots of choices.

These BOM's are for a full build including bridge rectifier and filter capacitor (not necessary for DC power supply) and an onboard 7808 regulator, which is not necessary for a DC supply up to about 12 VDC. These components should probably all be included for use with an AC supply however.

I can add a pdf version if anyone needs that option. Rod

Rod: Can you piece together a short video? I'd love to see this in operation. Please demonstrate the adjustments to timing with the pots.

Thanks!

  -- Leo

Consolidated Leo posted:

Rod: Can you piece together a short video? I'd love to see this in operation. Please demonstrate the adjustments to timing with the pots.

Thanks!

  -- Leo

Bad timing Leo; I just took the breadboard circuit apart, and my first order of boards has not arrived just yet. Once it does I will be happy to assemble one and run a short video for a demo.

I am also attaching the Excel spreadsheet for finding the correct value of R7 ballast resistor for the Vcc voltage level and the led intensity desired.

Cheers,

Rod

Got my first order of boards for this project today, and got one built. Works quite well:

I hope that video has uploaded OK. The red release timing was set to minimum for the video but it can be adjusted up to more than 30 seconds with the trimmer pot. The yellow delay is set to 10 seconds but that can be changed also.

Seems to work very well. This is an early version and lacks provision for an LM78xx voltage reg. But the version uploaded earlier above has the reg provision.

Rod

Rod, can I get you to send me the Diptrace files for this one?

gunrunnerjohn posted:

Rod, can I get you to send me the Diptrace files for this one?

No problem John, I will email them to you shortly.

Rod

So I have encountered an unanticipated problem with this first board build.

All my testing on the BB was done using a momentary pushbutton switch to simulate block occupancy, and I think RTR12 used the same idea. Now with this first board build I was experimenting leaving the BOD contacts connected for an extended time, like a train travelling through the block. I found that when you release the BOD, the red signal goes immediately to green, surprisingly.

It looks to me like the timing sequence starts as soon as the BOD contacts are tripped, instead of initiating when they are disconnected. Thus, when the BOD is opened, the release timings have already expired, and it goes straight to green. Not as we intended at all.

So anyone who is planning on ordering boards using the gerbers posted earlier, better hold off until we get this solved. For anyone who has already ordered boards, maybe see if you can cancel or put your order on hold. My apologies for any inconvenience. Hopefully we can get this solved quickly.

If anyone has any advice as to a resolution, that would be appreciated also.

Rod

The faint keyboard sounds are me deleting that set of files for the old boards.

Well things may not be as bad as I feared. RTR12 just rebuilt his breadboard circuit to the exact same circuit as the board I built, and reports that it worked perfectly, including the use of extended BOD triggering.

So it seems that I may have a flakey component, perhaps the 556. Planning a bit more testing tomorrow including a new 556, and go from there. 

Rod

Interesting, I wonder what's different?

Different times set. If the trigger doesn’t go high 10 uS before the time is up...

They must be using different times.

GRJ & cjack, What's different is definitely the $64 question? We are trying to figure it out. Quite puzzling. 

I am using 1 meg pots only for the red and yellow timing. I don't have the fixed resistors installed as shown in the drawing. Rod has these on his PCB I believe, but I don't see how that could be a problem either way?

I've tried different values for each 1 Meg pot along with several timing combinations for red and yellow, each one longer, shorter, same, different block trigger times (with the push button) etc. and all seems well here so far. Tried activating the circuit when they yellow was on. I can't seem to duplicate the problem?

The only quirk I have is when first powering up the bread board, without activating the block detector switch, the yellow comes on for a short time and then switches to green (default state) as it should be with no block activation. It then waits patiently for the block activation switch to close. Seems like this has happened in a few of the circuits we have tried for this project. I suspect this would probably not be noticeable when one was first powering up their layout. 

cjack posted:

Different times set. If the trigger doesn’t go high 10 uS before the time is up...

They must be using different times.

Microseconds? 

It's just that the trigger has to be shorter (by 10 microseconds) than the monostable time or the output will remain high until the trigger goes back high. And I thought that the setting differences and block signal time between the two boards tested might by why only one seems to work.

I'm confused about D2. What is it for?

Good question on D2. Rod might be able to provide a better explanation? But, as far as I know D2 was on the original schematics when we started trying these circuits and was just left in place. It was labeled 'Negative Recovery'?  Honestly, I never thought to remove D2 to see what happened, but you have now given me the idea to give that a try. 

I've tried several times today to make this circuit fail and so far it still works fine no matter what I do. Earlier, I accidentally turned the red timer pot (multi turn trimmer) down too far and got some odd results. Thought I had broken the pot or shorted something out? Checked and the pot set to 0.1 ohms. Reset to around 100k and all was well again.

I am using a bread board with 1 meg pots only, no low limit resistors installed ahead of the pot as shown on the schematic. I believe Rod does have the 200k minimum resistor installed. He's using a PCB made from the schematic. 

Well the beat goes on, but no resolution. I swapped in a new 556 but it behaves about the same way. And it is not consistent. Mostly it works as it should. But on occasion when the BOD is jumpered the green led stays on, it does not go to red. Then perhaps after 15 or 20 seconds, with nothing else going on, it will switch to red, and then after the BOD is opened it will time out normally.

Today I am going to build up a new board and see what it does. I must have a flakey component or connection on this board, and it's just faster to build a new one. If the new one works properly, guess where this one is going to wind up? Haha. I am also communicating with Rob Paisley and I plan to ask him what the negative recovery diode D2 actually does.  I have not seen anything like that on any other 555 or 556 schematic, or in any datasheets. In response to my first email to Rob 2 days ago his first question was; is D2 installed, and is its polarity correct.

Rod

cjack, I just did some experimenting with D2 and it does seem to serve a purpose in the circuit. 

With D2 in circuit you can hold the block detection contact closed as long as you want. When released the red then goes through it's complete cycle, then yellow cycles, then green.

With D2 removed, a momentary contact closure of the block detection device results in a normal cycle, red, yellow, green. But, if you hold the block detection contact closed longer than the red's timing cycle, when block detection contact is opened it goes immediately to the yellow cycle and then to green when the yellow cycle completes.

So, with D2 removed from the circuit, depending on how long the block detection contact is closed, the red cycle is either shortened or eliminated after the block detection device's contact opens.

Hope that makes sense...

Thanks I see that now with your explanation. The diode holds the DSC input low so that the 556 can't time out.

Rod Stewart posted:

Well the beat goes on, but no resolution. I swapped in a new 556 but it behaves about the same way. And it is not consistent. Mostly it works as it should. But on occasion when the BOD is jumpered the green led stays on, it does not go to red. Then perhaps after 15 or 20 seconds, with nothing else going on, it will switch to red, and then after the BOD is opened it will time out normally.

Today I am going to build up a new board and see what it does. I must have a flakey component or connection on this board, and it's just faster to build a new one. If the new one works properly, guess where this one is going to wind up? Haha. I am also communicating with Rob Paisley and I plan to ask him what the negative recovery diode D2 actually does.  I have not seen anything like that on any other 555 or 556 schematic, or in any datasheets. In response to my first email to Rob 2 days ago his first question was; is D2 installed, and is its polarity correct.

Rod

Maybe you could post a hi res picture of the built up board and other eyes could check it out for accuracy. Might help.