help with detecting an electronics component - Page 1
Forum section: electronics / beginners

author: m4rtin
author_rank: Regular Contributor
timestamp: September 24, 2015, 04:28:55 pm
content: What kind of component is damaged on the imagehere? A SMD 20 ohm resistor?

author: singapol
author_rank: Frequent Contributor
timestamp: September 24, 2015, 04:45:37 pm
content: Looks like a PTC resistor 20 ohm?

author: Falcon69
author_rank: Super Contributor
timestamp: September 24, 2015, 05:08:06 pm
content: that is a resettable fuse. 200mA

author: alsetalokin4017
author_rank: Super Contributor
timestamp: September 24, 2015, 08:51:10 pm
content: Not any more!

author: m4rtin
author_rank: Regular Contributor
timestamp: September 24, 2015, 10:42:01 pm
content: Quote from: Falcon69 on September 24, 2015, 05:08:06 pmHow do you know that this is a resettable fuse? How do you tell a difference from SMD resistor? I mean what should I check in order to be able to identify the component next time myself. In addition, does 200mA mean that once the current is >0.2A, the resettable fuse is tripped and the resistance of resettable fuse will increase in orders of magnitudes?Quote from: alsetalokin4017 on September 24, 2015, 08:51:10 pm

author: AF6LJ
author_rank: Unknown
timestamp: September 24, 2015, 10:46:36 pm
content: I agree it looks like a resettable fuse to me.

author: sleemanj
author_rank: Super Contributor
timestamp: September 24, 2015, 10:52:26 pm
content: Quote from: m4rtin on September 24, 2015, 10:42:01 pmIt just looks like one, having the semi-circular cut outs on the end is common with smd PTC and with smd LED, it's not an LED.A google image search gets us here:http://uk.farnell.com/te-connectivity-raychem/microsmd005f-2/polyswitch-smd-1210-0-05a/dp/1345915which is a 0.05A and has the same markings except the number, and if we apply that pattern we can see that yours is 0.2AQuoteYes and no. It will require substantially more than 200mA to trip (or a smaller amount more for a longer period of time), but it can pass 200mA. Take a look at the datasheet in the link above, in the performance ratings, you can see for that "50mA" fuse, it takes 150mA to trip it at 20 degrees ambient temperature, and the time to trip is 1.5 seconds at 250mA (20 degrees again), so you can see the overload needs to be substantial to get any meaningful trip-time. It we are talking about a pure short circuit, no problem, a few amps is going to trip it in a flash, if we are talking about just drawing a bit more current than usual, you might be there for a long time waiting for it to go.

author: DimitriP
author_rank: Super Contributor
timestamp: September 24, 2015, 10:55:08 pm
content: Quote from: m4rtin on September 24, 2015, 10:42:01 pmIf you knew the manufacture's logo , and that the company is poly switch and they are in the circuit protection business, you would have no trouble at all whatsoeverhttp://www.digikey.com/product-detail/en/MINISMDC014F-2/MINISMDC014FCT-ND/1045846

author: DimitriP
author_rank: Super Contributor
timestamp: September 24, 2015, 11:05:29 pm
content: QuoteOk, I like that method better

author: Falcon69
author_rank: Super Contributor
timestamp: September 25, 2015, 02:29:07 am
content: Quote from: m4rtin on September 24, 2015, 10:42:01 pmBecause I have lots of those exact ones in my Parts Bin. They are made by TE Connectivity/Rachem.http://www.mouser.com/ProductDetail/TE-Connectivity-Raychem/NANOASMDC020F-2/?qs=sGAEpiMZZMt8Ji9PfVTQzHcktPAFfzlpZFyge4QdWIE%3dThey are available in 9v, 12v, and 24v versions in 1206 and 1812 SMD size.