Saturday, July 11, 2009

Belated files

Very belatedly getting around to posting these.

The Eagle CAD files for the relay driver board is now posted at


Winston said...

Yay, thank you very much Michael!!!

Winston said...

I had a chance to look at these files in Eagle; according to the Olimex rules, I had to fix the drill sizes of the via's and make some small changes to the some of the clearances around the ICs. I still get errors for the width of the track connecting pins 17+18 of SV1 to the leftmost pin of JP11 and also on the dotted line running up the left edge of the board. Olimex say to not ignore errors, I'm guessing that since you used BatchPCB, they didn't have any problems with it. I guess I'll try submitting it and see what they say!

Thanks again for uploading these!

Winston said...

One more thing, any chance you could elaborate on some of the parts? The parts list exported by Eagle isn't very clear. Some things I can easily find on DigiKey, but other stuff such as the diodes & transistors are harder to find.


Winston said...

After some digging, I think I have figured out a parts list for the board. I hope the formatting works out when I post this, but I had to do a spaces-to-tabs then convert tabs to &nsbp; to try to maintain the columns.

This is almost all of the parts that the Eagle parts list shows, except for JP1 and JP10 (because I already have those!).

If anyone sees an egregious component mistakes, please post here and let me know!

Part                    DigiKey #                      Description

C1-4                  478-1239-1-ND             CAP CERM .1UF 10% 16V X7R 0603

D1-8                  B340A-FDICT-ND      DIODE SCHOTTKY 3A 40V SMA

IC1                     DS2482S-800+-ND     IC I2C TO 1WIRE BRIDGE 16SOIC

JP2-9                 WM7877-ND                CONN TERMINAL BLOCK 2POS 3.5MM

JP11-20             WM7878-ND                CONN TERMINAL BLOCK 3POS 3.5MM

Q1-8                  FMMT491CT-ND        TRANS HP NPN 60V 1000MA SOT23-3

R1,3,5,7,9,11,13,15     P1.0KGCT-ND         RES 1.0K OHM 1/10W 5% 0603 SMD

R2,4,6,8,10,12,14,16    P10KGCT-ND          RES 10K OHM 1/10W 5% 0603 SMD

R17                    P120GCT-ND               RES 120 OHM 1/10W 5% 0603 SMD

RN1-2                Y4101CT-ND               RES ARRAY 100 OHM 5% 4 RES SMD

SV1-2                S7121-ND                      CONN HEADER FMAL 36PS.1" DL GOLD

U$1                   MAX3485CSA+-ND     IC TXRX RS485/422 250KBPS 8-SOIC

Michael said...

My parts list included:


Anonymous said...

Just curious, how the PCBs are expensive in the different parts of the world? Two pieces of this relay board PCB costed me 1800RUB (58 USD) including local delivery. I live in Moscow, Russia.

Anonymous said...


What type of relay do you use in this project?


Michael said...

I got my PCBs from Olimex and they were ~ $USD35 from memory plus shipping.

I used a bunch of FR6 relays. Wild overkill (they switch 30A @ 250V) but they're cheap and fairly reliable.

Winston said...

I just put an order into BatchPCB for 2x of the board and it cost me ~$48 (incl. shipping & handling). I would have used Olimex, but they are shutdown over August for vacation!

I'm waiting on this and a DigiKey order for the parts, then the fun begins! I have two buildings in the northern US that I need to monitor the heating (lock out) & interior/exterior temp over the winter. Last year we had several heat-outs in 5F weather that almost froze the place up!

The plan is to have the NGW100 monitor the place and send me a email if the boiler(s) lock out, or the temp goes out of range.

Winston said...

The PCBs came back from BatchPCB yesterday, so I spent last night building one of the boards out. It took a while, but it works!!! (at least the 1-wire part, I haven't tested the relays yet and I'm not sure I have anything to test the SPI or RS-485/422 parts).

It was all pretty easy to do using a fine tipped soldering iron, except for the resistor networks which were a real pain because they are so small and there are 8 tiny solder pads under it! Some of those 0603 parts are tiny too, I definitely recommend a magnifying glass-on-a-flex-stem.

Using a multimeter, I tested each component as I put it down and found a couple of dry joints that needed reheating and also a short (on the one of the resistor networks). I didn't have a good way to test the ICs (other than to try it!).

I had bought some solder paste which was great for the ICs, after struggling with the RNs it occurred to me to print out the board layout and use a sharp blade (i.e. a scalpel) to cut out a mask so I could smear the paste over the solder pads. For board #2, I will get a piece of thin, clear plastic (i.e. soda bottle thickness) and carefully cut out masks for the RNs, SO-16 and SO-8 pads.

If were to make these boards again, the only change I'd make is to move the DS2482-800 up a bit (maybe 3/32") because it's a little close to JP11 and JP12 -- it fits, but they practically touch.

Michael, many thanks for making these schematics available!!! It's a very clever design to have the relay board straddle the NGW100 and plug into the J5/J6 expansion connectors and pick up the 12v from J16.

Winston said...


I found an error in the Eagle files for the relay board. Pin 1 of the MAX487 is mislabeled as RELAY-RX whereas pin 18 on the header coming in from the NGW100 is actually RELAY_RX, so they're separate nets in Eagle and consequentially there's no track connecting pin 1 to pin 18 on SV2. It's an easy enough fix in Eagle and for my already fabricated board it's a quick green wire fix to connect pin 1 on the MAX487 to pin 18 on SV2 to make this work.

The relay board works really well for 1-wire devices, but any thoughts on:

1) Is the VCC supply on the 1-wire branches enough? (considering it supports 8 networks?) or does it need a voltage regulator to take the 12v and drop it to 5v?

2) ESD protection, I'm running this over CAT-5 wiring via a home patch panel, so I've got wires running through ceilings, crossing 120v AC wires etc. I've been looking at either a Dallas DS9502 or a SL05T1 which both seem to be designed for a data network.