Using IoTT Shields with EX 8874 (Video

[@Trains-With-Shane]

Thank you for these diagrams, Hans! It looks like the extra converter on the EX 8874 really makes things complicated for IOTT stick users if they want to have wired LOCONET. I think i'll just stick with my standard motor shields for now.

[@IoTT]

Well, it's not really complicated, just a little bit of a hassle. And important to know about it so you don't run into problems. For the EX 8874 it would be an easy fix to put the DC/DC converter at 5.1V output to the 5V rail in the next revision, and add a protection diode in the path to make it safe against back-feeding.

[@paulscarlett4346]

Well done -- The first part (Arduino only) should be viewed by all Arduino users as it is the clearest review of power I have seen. For IOTT fans the rest is just as great -- clear and concise. Suggestion for store or 3D library -- a 3D printed blocking plug for barrel jack. Alternatively I suggest using a empty barrel jack connector with no wires attached.

[@geesharp6637]

Yes, a barrel dummy plug would be nice.

[@IoTT]

Thank you. A blind plug would be easy to do. Maybe I add one to the final EX 8874 frame as there is no need for it when only using IoTT boards ;-))

[@smokinbigdavebbqandtrains]

Just received my IOTT items today. Stick, Red Hat and Aux shield. Already have the Mega and 8874. Can't wait to get this set up and running. Appreciate the videos and knowledge!

[@scentgrasslakerailway]

Great information Hans!

[@IoTT]

Glad it was helpful!

[@trainguy0]

Thank you for the video. I have a much better understanding of how the 8874 motor shield fits in the system.

[@IoTT]

Thanks, that was the goal ;-)

[@BriansModelTrains]

Thank you and great diagrams.

[@IoTT]

Thank you. Glad you like them!

[@billflude5204]

Great explanation - very clear - thanks Hans!

[@IoTT]

Very welcome.

[@geesharp6637]

That really explains a lot and helped clear up some concepts I was missing. These combination diagram would be great to include on your IoTT web site. I have a few assumptions to confirm. #1, the Redhat v1 doesn't change the picture too much except to merge the AUX shield and current Redhat v2. #2, your 5amp power shield doesn't impact this in any way since it has it's own power input that must always be used. Thanks.

[@IoTT]

Thanks. I probably just put a link to the Video on the web page. Just the diagrams without explanation will probably not do the trick. 1) Correct, the original RedHat was RedHat and DCC AUX on one board. Conceptionally it is the same, so the problems with the EX 8874 are the same. 2) Correct, the IoTT Powershield works like the standard motorshield, no strange voltage on VIN. But it does allow for single DC supply setup as there is a jumper to feed the DC voltage to VIN, it even has an onboard reverse voltage protection for that purpose. So, if you want to use the Powershield along with the old motorshield for CV programming, you can do that with one single power supply.

[@geesharp6637]

@@IoTT So if I only had a UNO, power shield and redhat, I can use only one powersupply somehow? Isn't 12-15v a bit high for the uno?

[@IoTT]

Yes, assuming it is the old RedHat with the onboard DC/DC converter. There is a jumper next to the LED labelled VIN. If closed, it connects the power supply to VIN, through reverse voltage protection. Make sure all pins are properly inserted in all boards and it works exactly the same way as described in the video. If you have a new RedHat, you need to add the DCC AUX shield for the same function.

[@ewkco]

Thanks for the in-depth info on powering the DCC ex stack. Just ordered the DCC-aux board and red hat shield. I have the elegoo mega and DCC-ex 8874 motor shield. Any other changes needed to get this running?

[@user-fs9jm5sw2r]

This is a GREAT video. Now understand the need for the DCC AUX Shield. A question. Its common on DCC++ EX to have a wifi shield ( to allow withrottle, etc), and due to smaller size, that shield often ends up at the top of the stack. If adding a red hat shield that adds loconet wifi, is it also necessary to have a wifi shield for DCC++EX? If so, useful to add that to the stack of examples i.e. how do things get powered on top of a red hat shield i.e. MEGA -> 8874 -> AUX -> REDHAT ->WIFI SHIELD

[@user-fs9jm5sw2r]

e.g. using the recommended makerfabs wifi shield atop the stack

[@IoTT]

When using the IoTT Stick on top of either DCC AUX or RedHat Shield, Wifi is provided by the Stick. It has WiThrottle, Loconet over TCP and MQTT servers and provides the web pages for configuration. You can connect to it with JMRI and other software, and with EndingDriver or WiThrottle.

[@robleathley6024]

Great video Hans explaining the many power options available. I'm just getting to this now as we were busy with a model railroad show on the weekend. Just one question for you. Does anything have to change if you add a second PowerShield to the mix? In other words, stacked from bottom up: Arduino Mega, PowerShield A, PowerShield B, RedHatV1. All this to take advantage of the capability of additional power districts. PowerShield A for district 1&2 and PowerShield B for district 3&4. Just plug a separate track power to each PowerShield and ensure that the jumpers on each PowerShield are set correctly?

[@IoTT]

Thank you, Rob. Yes, it is just plug in. In fact, you can stack up to eight of them if you are using DCC EX 5. For small scales with relatively low power consumption, it is possible to share the same DC supply. For larger currents I would suggest using individual power supplies for each board. And yes, of course you need to use different pins and configure them in the DCC EX setup accordingly.

[@robleathley6024]

@@IoTT Thanks Hans. That is what I thought. Appreciate the confirmation. I have a 10 amp, 12volt power supply split into two outputs, one going to each PowerShield. I don’t think that will cause me problems.

[@user-fs9jm5sw2r]

Separate question for Hans. Your excellent PurpleHat shield. It's for HO scale, Would you consider an OO version. I'm wondering/confused if OO/HO trains use the same diameter axles/wheels as OO/HO, so don't need to be treated differently, BUT due to the different scales (3.5mm vs 4mm) doesn't that mean that the calcs for speed (MPH/KMH) need a different constant/factor in their computation? Also wondering about the possibility of different sized wheels/axles. Would adding optional params, defaulted to HO to allow users to adjust for wheel/axle sizes/scales be a nice addition to the PurpleHat?

[@IoTT]

The PurpleHat has a function to measure the wheel size. You push it a defined distance and it calculates the diameter based on the measured turns. Simple. It works for all scales.

[@user-fs9jm5sw2r]

respect, this is great/happy to use. I have ordered a purple hat. BUT. This will allow accurate real speed calcs, but surely the SCALE speed calc depends on the scale? Can you change the scale/the constant you multiply the real/actual speed by scale to work out scale km/h / scale mph so that I can get /set a more accurate scale speed for the locos I have. I wish to calc/limit the locos to their official scale speeds, without having to adjust all the calcs. Is it possible to expose that constant as a config file param and/or via the GUI. Shouldn't be that hard to program, I speak from 26+ years experience of coding experience. If I'm not understanding the calcs, excuse my beginner ignorance, is there somewhere in your excellent instructional videos I can better understand/is there something in the documentation/where can I look in the source code on GitHub etc to see how the calcs are done? If you're not using scale in the calcs then I dont understand why there are HO, N and G scale versions of the purple hat. I accept due to different sizes there may be other variations in the purple hat.

[@IoTT]

Videos #116, #122, #123 should probably answer most of your questions. All PurpleHat videos are included in the PurpleHat playlist. Of course, you have two settings. One for setting the wheel diameter to measure the real life distance, and then a scale selector to calculate the scale distance and speed from the measured distance and time. Simple application of basic physics ;-)

[@rolandminshall7949]

What would be the recommended power sourcing if I am using a Red Hat Shield, Aux shield and TWO EX8874 boards?

[@IoTT]

Use a DC power supply from 12 to 16V to power the RedHat (via AUX for the new rev RedHat). Then use a regulated DC supply for the track voltage on the EX8874. If it has enough current output, you can use a single supply for both 8874s, but I probably would use two individual ones. Make sure to cut the VIN trace on the 8874s.

[@stufan77]

I have a DCC-EX command center built from Arduino Mega and Standard Motor Shield. The Vin connect is cut and I use two power supplies but I didn't like this solution. So I bought DCC AUX shield and what I am not sure is shall I restore the Vin connect i.e. not be cut? If yes, what is the best way to do it - is it enough just to solder it thus restoring the connection

[@IoTT]

Assuming you cut the VIN trace on the motorshield between the two pads next to the Arduino header, you can simply restore it by soldering the gap. That is good for more power than the standard motorshield typically can deliver. After restoring the connection, you can use a single power supply the the DCC AUX DC jack und supply it with up to 18V for your track voltage. The DCC AUX shield then takes care of supplying 5V and VIN to the Arduino board, bypassing the LDO on the Arduino board. Just make sure all pin header pins are correctly connected to the board below.

[@stufan77]

@@IoTT Thank you very much! That's what I needed as info

[@roydom5]

When you need to renew the router credentials in the M5 stick what is the best way? Do you need to switch it into AP? I have tried but the buttons on the side don’t seem to help!

[@IoTT]

If the current router is not active, it will automatically branch to the captive portal and you can set it up like a new IoTT Stick. If you want to connect to another router while the old one is still available, you can delete the old settings by clicking the power button rapidly about 4 or 5 times. That should restart the Stick, erase the Wifi settings, and it will branch into the captive portal, so you can set a new router using your smart phone. See here for more information and the flow diagram for connecting to Wifi: myiott.org/index.php/iott-stick/user-manual/iott-stick-core/wifi-configuration