Sumersible cable for aquarium temp control - Page 1
Forum section: electronics / projects

author: ElektroQuark
author_rank: Unknown
timestamp: June 17, 2014, 06:18:18 am
content: Hi,I need a sumersible cable to sense temperature in an aquarium with a DS18B20 sensor.I know nothing about cables. Principal requirements are:- Waterproof- Flexible- Three cores- Low diameter- Cheap if it's posibleI first though on silicone but I don't really know.Any advice?

author: nowlan
author_rank: Frequent Contributor
timestamp: June 17, 2014, 07:17:39 am
content: I would have just cut the one of this.Aquariums Digital Water Thermometer with Waterproof Remote Sensor$3.61

author: Paul Price
author_rank: Super Contributor
timestamp: June 17, 2014, 08:26:39 am
content: Pot the sensor in casting resin, epoxy or just cover with an air-curing silicon rubber coating(get the high quality GE Silastic type of silicon rubber).

author: ElektroQuark
author_rank: Unknown
timestamp: June 17, 2014, 09:40:03 am
content: I have it working with a generic cable (salvaged from a PC mouse) in the development system. The sensor is epoxied.I want to use the apropiated cable for the working systems.

author: TerraHertz
author_rank: Super Contributor
timestamp: June 17, 2014, 03:16:08 pm
content: PVC is water permeable. For instance if you put standard CAT-5 cable in underground conduit, after a while it will stop working as moisture diffuses through the thin PVC insulation into the internal cavity, and alters the impedance characteristic of the pairs.CAT-5 and phone Cables rated for underground use have a thick high density polypropylene (polyethylene?) sheath, that is water impermeable. The phone type often has the internal airspace filled with silicone gel too.Then there's the cable type used with mains-powered garden pond pumps. I don't think that is silicone either, but not sure what it is.Why don't you phone up a local cable supplier and ask them what they have?

author: Towger
author_rank: Super Contributor
timestamp: June 17, 2014, 04:47:18 pm
content: Quality mains garden pump cable is more often than not 'HO7'. You can pick it up on ebay, but I find the local wholesaler is cheaper.

author: Rick Law
author_rank: Super Contributor
timestamp: June 17, 2014, 06:02:49 pm
content: A different point of view:It is just"cable to sense temperature in an aquarium", why over engineer it.In fact, If it is low volt sensing (like in the below 1V range) I would use what I strip out from a cat 5 cable (cheap) and throw them out every other year.The algae (and other bio-matter) built-upis going to be far worst than water leakage. If it fails, it is not going to kill the fish. It will just be your alarm clock that it is time for a new cable. (Not like an AC heater, if that fail, you could have fish soup.)If/when that fail, you just get some crazy reading --- the fish can't read anyway, it will merely be a alarm call for you to throw the cable out and make another one.

author: JohannP
author_rank: Contributor
timestamp: June 17, 2014, 06:16:30 pm
content: EdoNorkWhy not try one of these for the DS18B20?http://www.ebay.com/sch/i.html?_trksid=p2050601.m570.l1311.R3.TR11.TRC1.A0.H0.XDS18B20&_nkw=ds18b20+waterproof&_sacat=0&_from=R40Best regardsJohann

author: ElektroQuark
author_rank: Unknown
timestamp: June 17, 2014, 06:45:30 pm
content: I have a bunch of DS18B20...But this option seems cheaper than buy the cable only. Thank you.On the other hand, I would like to know what colud be the right cableQuote from: JohannP on June 17, 2014, 06:16:30 pm

author: theatrus
author_rank: Frequent Contributor
timestamp: June 17, 2014, 09:14:47 pm
content: Quote from: Rick Law on June 17, 2014, 06:02:49 pmCopper is highly toxic to any invertebrate. Salt water also destroys everything without abandon. Extra redundancy of insulation is key.

author: Rick Law
author_rank: Super Contributor
timestamp: June 18, 2014, 03:12:06 am
content: Quote from: theatrus on June 17, 2014, 09:14:47 pmLast I check, most if not all fish are vertebrates. But point taken. If copper oxide do leak out of a cracked wire, there could be some issues there.

author: theatrus
author_rank: Frequent Contributor
timestamp: June 18, 2014, 03:17:57 am
content: About 90% of the biological organisms in my salt water setup are highly sensitive to copper(I only have three small fish)

author: NiHaoMike
author_rank: Super Contributor
timestamp: June 18, 2014, 03:29:17 am
content: What about attach a sensor to the outside of the tank?

author: rob77
author_rank: Super Contributor
timestamp: June 18, 2014, 03:35:43 am
content: i would just buy ANY waterproof cable for low voltageor slip a regular low voltage cable into a silicone tubing.btw.. the above mentioned idea of sensing the temperature at the outside wall of a fish tank is also a good way.