Combined Power & Data Cable  - Page 1
Forum section: electronics / projects

author: Jobadro
author_rank: Newbie
timestamp: March 29, 2020, 03:52:49 pm
content: Hey Everyone,since I have a lot of time lately due to our current global medical situation, I finally wanted to start a proper Project.I want to build some hit reactive drum lights. There are some projects already out there, but I want to do it a little bit more professional. (custom PCBs; proper cases, cabeling, connectors)I have planned to put a MCU on every drum (5 in total, headroom would be very nice). It would be responsible for controlling an adressable LED strip (planning to use the BTF2815 at the moment) and reading the signals of a piezo sensor, wich is mounted to the drum head.Now comes the tricky part. I want to configure those MCUs (LED color, sustain time, whatever else I come up with) from a MCU on the end of a bus, that connects them all. It would be a nice feature, to be able to transmit the drum hits to if configured, so all drums light up, when I hit the Basedrum for example. For this reason I am planning to use a can bus.My problem is, that I also want to power everything through the same Cable. I think, I would need 12V and 5A to be on the save side. The total cable run of all the daisy chained devices would probably be 6m long. I have been looking for some hours and have not found any cable, that could transfer 5A and a CAN bus reliably. D-SUB is standard for CAN, but i think it couldn't handle the power from what I have read. Cables that could, don't have twisted pairs. There are some hybrids, but they are all custom and pricy. I would like to use something commonly available if possible. Most of that suff does not give you a current rating and you could only guess what is inside those cables. I would also be fine with putting the Connectors on myself if necessary.It would be cool if someone knew the perfect cable, but I would also be open to change the protocol or step down the voltage if that helps.I hope, I have given you the information you need and that someone can give me some inspiration.With kind regardsJobadro

author: Renate
author_rank: Super Contributor
timestamp: March 29, 2020, 04:27:25 pm
content: CAN is a fine standard, but not at all to be found around music.For lighting DMX512 is a very typical thing.For the drum interface MIDI would be a standard thing.The question is if the latency of all this would be unacceptable.You could make it so that you could have things both ways.Have the drums output MIDI but also interface directly to the lights.Have the DMX512 control the lights too.

author: Jobadro
author_rank: Newbie
timestamp: March 29, 2020, 04:59:12 pm
content: Thanks for your reply Renate.I have thought about MIDI and DMX, but from what I know, it is not realy used to broadcast to all bus members. They would either have to listen to all adresses or a central hub has to distribute the information between the members. I think, a can bus would be more practical in this case. I also don't care about compatibility between my system and MIDI/DMX. If I want to Implement that later on, I could easily use the configuration unit as a bridge.This would also not solve my problem with the power distribution from what I know. The latency should be invisible to the human eye, when I communicate between Drums.

author: roman.isaikin
author_rank: Contributor
timestamp: March 29, 2020, 06:08:48 pm
content: Cat 5/6 twisted pair may be an option, it is very cheap, connectors is not hard to crimp with the proper tool, which is also affordable. As for the current, you can go higher in voltage, to 48V for example and put dc-dc converters at each node.

author: mansaxel
author_rank: Super Contributor
timestamp: March 29, 2020, 06:28:17 pm
content: Quote from: Jobadro on March 29, 2020, 03:52:49 pmLAPP Group Servo cable Type 7072400. 2 cores 1mm2and 4 pairs 0,25mm2. Outer diameter 8,8mm.Data sheet.

author: mariush
author_rank: Super Contributor
timestamp: March 29, 2020, 06:56:42 pm
content: You could use cat5e/cat6/cat6a cables (patch cords are mass produced and cheap and flexible) which give you 4 pairs of wires.You could use one or two pairs for voltage ... I'd suggest using dc-dc converters that can do up to 24v ... would allow you to use cheap laptop adapters that output 16.5v or 18.5v but could also use a standard 24v power supply to power everything if needed.Maybe consider rs232 / rs485 at some high baud rate like 192000, or even higher, should be fast enough for your needs... with short cables you could use 5v ttl for the data transmission.maybe even use a rs485 hub/switch and give each device a unique address...

author: Jobadro
author_rank: Newbie
timestamp: March 29, 2020, 08:03:50 pm
content: Thanks for all the replies,I like the idea with the servo cable. Maybe I could put some 4 pin xlr connectors on them. They are pretty cheap and I don't use them anywhere else. Better suggestions are always welcome. I will also look into the DC-DC converters. I have already thought about cat cables, but I don't like the standart RJ45 connectors. I think, they are a bit flimsy for my taste.Thanks for the all the suggestions.

author: mansaxel
author_rank: Super Contributor
timestamp: March 29, 2020, 08:58:32 pm
content: A 4-pin XLR with a CAT5 cable soldered with, say, blue pair to 1+2, and the other three pairs in parallel on pins 3+4 (like "whites" on 3, "fullcolor" on 4, of course) could work.Another idea, look for a data+control cable that isn't heavy-industrial like the Lapp one. Belden 1502SB Multi-Conductor - Multimedia Control Cable could fit really well, having one shielded AWG22 pair and one unshielded AWG18 pair.Datasheet.

author: Jobadro
author_rank: Newbie
timestamp: March 29, 2020, 09:36:15 pm
content: Quote from: mansaxelThat one also looks nice. I will look into the cables and connectors some more. For now I know, that I can push data and power through one cable one way or another. I will start with the circuits and programming for now. The final cabeling can wait for when the rest works. So I have enough time to make up my mind about that. I could update this if you are curious about the progress.