Flat power resistor - Page 1
Forum section: electronics / beginners

author: senso
author_rank: Frequent Contributor
timestamp: June 11, 2015, 09:48:24 am
content: Good morning, looking for another component, this time I'm on the look for flat power resistors, the idea is to make a big heated plate to remove broken digitizers from tablets and laptops, my idea was to use the typical cylindrical power resistor that have a built in heat-sink(photo attached in the end).But given that the aluminium slab will have around 30x40cm those would be too localized I think, so I tried to find some nice big planar power resistor, like the ones that are used in this type of hot plate:http://www.aliexpress.com/item/free-shipping-high-quality-LCD-separator-Machine-Hot-Plate-for-Screen-Glass-Repair-iPhone-5-Galaxy/1278138825.htmlI have one and the resistors are two rectangular pieces, each half the size of the heat-plate, but I can't find anything as big as those at Mouser/Digikey/Farnell.Any ideas where to find big power resistors, the total heating power needs to be around 1-1.5kW for fast heating, the max temperature needed is just 80ºC.

author: Cliff Matthews
author_rank: Unknown
timestamp: June 11, 2015, 11:18:12 am
content: Remove handles, clamp on a thick sheet of aluminum, and you're in business with a 10amp Variac (adjustable auto-transformer).Use a thermal probe to find Variac's sweet spot for it. It's a nice piece of kit for any bench..

author: matseng
author_rank: Frequent Contributor
timestamp: June 11, 2015, 11:39:54 am
content: Planar resistors then?http://www.newark.com/webapp/wcs/stores/servlet/Search?st=planar+resistors&catalogId=15003&categoryId=800000059511&langId=-1&storeId=10194

author: Cliff Matthews
author_rank: Unknown
timestamp: June 11, 2015, 02:39:13 pm
content: Those planar resistors are expensive! (almost as much as the unit specified). I suppose if one does a lot of this type of repair, that unit is worth it then.. Along-side all the micro tools, molybdenum cutting wire and special pastes, it's not too pricey.

author: tszaboo
author_rank: Super Contributor
timestamp: June 11, 2015, 02:57:57 pm
content: A reel of 1206 is like 6 eur, and a two sided PCB this size must be cheap at the local manufacturers. Bonus if you integrate the temperature controller in the middle. Get an intern to solder it.

author: zapta
author_rank: Super Contributor
timestamp: June 11, 2015, 03:22:42 pm
content: What's your target temperature? Is it to desolder or just to loose glue?

author: mikerj
author_rank: Super Contributor
timestamp: June 11, 2015, 04:33:53 pm
content: Maybe acontact grill elementwould be useable?

author: N2IXK
author_rank: Frequent Contributor
timestamp: June 11, 2015, 04:42:51 pm
content: Quote from: Cliff Matthews on June 11, 2015, 11:18:12 amSince it is a pure resistive load, a simple (and cheap!) incandescent lamp dimmer is all you need to control that thing. No need for a big expensive variac to do it.

author: Cliff Matthews
author_rank: Unknown
timestamp: June 11, 2015, 05:18:40 pm
content: Quote from: N2IXK on June 11, 2015, 04:42:51 pmTrue, but I'll take the Variac since it can be used on a thousand other issues

author: electr_peter
author_rank: Unknown
timestamp: June 11, 2015, 05:47:03 pm
content: If low temp is enough, search for "car/bus/truck mirror heater".

author: firehopper
author_rank: Frequent Contributor
timestamp: June 11, 2015, 08:07:12 pm
content: what about heated beds for 3d printers?

author: Cliff Matthews
author_rank: Unknown
timestamp: June 11, 2015, 10:11:37 pm
content: Quote from: senso on June 11, 2015, 09:48:24 amThick aluminum spreads heat evenly. Spread out 6 pasted 50-ohm 50-watt resistors wired in series with thermal sensing at the center and it should be quick enough at both 120 and 240v. I still think a flat pan is best on $$... You've just got to control the temp, have fun!