SSR vs Variac - Page 1
Forum section: electronics / beginners

author: Kakashi
author_rank: Contributor
timestamp: November 17, 2015, 12:46:43 pm
content: Will solid state relay do a "near" same job as an good old variac? Which one is better for AC voltage control and why?Need some variable AC voltage but thing is, where I live there are almost zero to none variacs. But you can find SSR almost anywhere...Don't know if an SSR will do a good job at controlling AC voltage(0-230V). If someone is willing to explain the main differences between the two that would be nice!

author: Simon
author_rank: Unknown
timestamp: November 17, 2015, 12:50:53 pm
content: no a solid state relay will only turn on or off. A variac will control the voltage from 0-max

author: coppice
author_rank: Super Contributor
timestamp: November 17, 2015, 12:54:45 pm
content: Quote from: Kakashi on November 17, 2015, 12:46:43 pmAn SSR is an isolated switch. A variac is a (usually) unisolated variable control. They have little in common.

author: mij59
author_rank: Frequent Contributor
timestamp: November 17, 2015, 01:09:49 pm
content: You probably meant SCR's (or a triac ) using phase angle control.Using phase angel control gives a non sinusoidal voltage across the load.

author: Kakashi
author_rank: Contributor
timestamp: November 18, 2015, 01:36:29 pm
content: @ShockIt's exactly as you said I need it for.Old stuff that don't know if they will blow up in my face or some project that require high voltage/current...I thought the SSR can somehow regulate the output voltage, by different input voltage 5-30V. Didn't know they were only for turning on/off.As for the bulb trick I do know of it, and been using it for years now. But I wanted something more "sophisticated".NVM though, I will continue to search for that elusive variacs that I can't find anywhere.Thank you everyone for your replies!

author: dom0
author_rank: Super Contributor
timestamp: November 18, 2015, 05:12:09 pm
content: QuoteAC lab supplies are also notable for being bloody expensive

author: oldway
author_rank: Super Contributor
timestamp: November 18, 2015, 05:28:46 pm
content: A variac is really a MUST HAVE.Don't forget to protect the OUTPUT (not the input !) of the variac with a fuse or a circuit breaker.

author: dom0
author_rank: Super Contributor
timestamp: November 18, 2015, 05:33:22 pm
content: You really want one of the small circuit breakers on the output, and a much larger (say 4-8 x IN) slow-blow fuse on the input (in case of problems with the transformer windings or shorts in the wiring).

author: mich41
author_rank: Regular Contributor
timestamp: November 18, 2015, 05:41:13 pm
content: Quote from: blueskull on November 18, 2015, 04:23:27 pmWater, 230VAC and NaOH? Sounds like scene from the Brainiac show

author: SeanB
author_rank: Super Contributor
timestamp: November 18, 2015, 06:05:32 pm
content: Just like our old generator test loads. 28VDC one was an old iron bed with steel strap springs, and the 115VAC one was a drum with 3 steel rods that you immersed in the salt water brew inside. Both could be driven to way past hot, though the bed was also capable of lighting a fire while the drum would just emit steam.

author: dmills
author_rank: Super Contributor
timestamp: November 18, 2015, 07:37:41 pm
content: Back in the day, early electrical stage lighting was controlled with series resistance in the form of "Piss pot dimmers", so called for the rumoured approach to refilling the things when they had boiled a bit too much off (Or at least that is what the Chiefs used to tell the apprentices).Usually a set of ceramic tubes with an electrode on a non conducting lever, and a bank of knife switches to route the dimmers to whatever loads needed dimming in this scene, in some versions the mechanics got notably sophisticated ending up with the (By this time air cooled resistance wire based) Grand Masterhttp://www.theatrecrafts.com/archive/documents/photo_grandmaster_01.jpgwhich I have actually had occasion to use.Regards, Dan.

author: dexters_lab
author_rank: Unknown
timestamp: November 18, 2015, 10:25:13 pm
content: Quote from: Kakashi on November 17, 2015, 12:46:43 pma SSR or solid state relay is just a switch, an electronic one, so just like a mechanical relay it will switch higher power circuits with a low power signal. Generally this might be switching mains voltage with a low voltage signal (typically 5-24v), there is no control over the switched input, it's simply on or off.a variac is an electromagnetic & mechanical device which acts like a transformer... so depending on it's configuration you can input say 240v ac mains and get a 0-240v ac outputyou mentioned your wanting to power up old devices with this, so i would say a variac is ideal and best suited for this... maybe they are hard to find in Japan, but here in the UK they are easily available. They do cost quite a bit to buy but are well worth the investment as they will probably last a lifetime and have many uses. I bought a Carroll & Maynell 5 amp variac a few years ago and it is very handy at times!