Nick, James, and Marq, JMRI does do a loop at the very lowest level polling for all declared inputs and passing outputs. So in that respect, it is like the...
Hi All, I have a problem with 2 of my 24 DCCOD's. While most of my units are sensitive in the 50K range, I have 2 that will not trip until the load is down to...
Mike, I don't know if there are any nominal readings. I doubt it. All of the schematics that I have seen for the ODs and DCCODs have never had any voltage...
Hello Mike, With no track power it would seem that the voltage would be zero at U1 pin 7 but there will be a little bit of amplified noise and some bias in the...
All event driven software systems such as Visual BASIC loop through the various input devises looking for a change in condition, however it is done at the...
Marc, Thanks for the insight. Since the resistor values seem to be identical for the gain in stage one between the good and bad cards, that seems to leave just...
Hi all, It turns out the chip itself did have a problem. This was confirmed by the testing Mark outlined, and also in swapping chips between two different...
Issue Resolved. The first stage of the LM324 was bad at pin 7 on both of my bad cards. Confirmed static DC voltage readings are nearly useless. Using an...
Below is a link to photos I uploaded to the group site. It shows a DCCOD repackaged to use SMT parts. It is not a project for the casual user. But if you are...
Mike, From what I have been taught about op-amps the voltage changes are so small and the gains are so high that you just can't say yep these are what your...
Mike, Again thanks for the info! SMT is usually less money because they are now being made in larger quantities. This was true ten or so years ago. rich! ... ...
Hello Mike, I think I found the smoking gun. On the top side, there is a trace that goes from the square lead of the current sensing transformer secondary to...
I'd like to see these with molex connector so they are a drop in replacement for the existing DCCOD on the ODMB. ... -- Seth Neumann Mountain View, CA ...
Mike: Interesting project. As Marc is noting on parts and trace placements I would look at the trace size for the DCC power to the transformer. It's possible...
Marc, Thanks, for your input. I think from a value point of view and not from a price point of view i will stay will the standard DCCOD. Also is a few extra...
Well How did that get there?!?! Thanks for spotting this Marc. I did a re-check of the nets and found this to be the only spurious trace. Since pins 1,2,3 are...
The parts were all purchased from Digikey. (I will Post the Bill of materials to the Files section of the group). The schematic and PWB was laid out using...
Mike, Check the data sheet for the LM324 about how to tie unused sections of the chip. I know many logic chips the standard is to tie them low or high...
group- correct me if I'm wrong, please! I thought the larger current would be in the primary ( from the track), inducing a voltage in the secondary, with...
With a small track current in the primary, you will get a smaller small current in the secondary - obvious... With a large track current in the primary, you...
Good observation Ken. I found the following link which describes the proper (and improper) methods to terminate unused pins on the LM324. The document is by...
We all seem to be speculating exactly how much current is on the secondary of T1, and accordingly the voltage it creates on R2. I believe D1 & D3 are to clip...
Mike: All that I was taught about unused gates even on TTL was to pull them to their lowest current state, usually down. Thus preventing oscillation. In...
How many have burned out because of the unterminated op amp? Zero. I am a bit surprised by the sensationalism of that document that TI published. On the other...
Hello Jim, The cost associated with adding additional parts is 3 fold. The actual part cost, the additional board space for the parts and traces that need to...
I noticed in the image there is a comment about soldering with a very pointed soldering tip. I personally use a solder station and the first thing I did when I...
Marc: Good comments, yes the multipliers with leaded parts. A little different with SMT board cost if square inches don't change the board cost doesn't unless...
... Two resources for those who may be interested. The first is a very good intro to SMT soldering, the second is an Apple video from way back showing how...
Marc, I completely agree with you about all of your observations including the forgiveness of the LM-324. One other thing that wasn't addressed is the response...
