| I made the mistake of never buying one for a reasonable price from Sweet Maria's back when they sold them, and now I want one ;) Anyone know a good place to get a reasonably priced and well performing variac? I guess it needs to be 0-140v output, 15A (if not 20, though I guess i should make sure my circuits at home can handle that). -F Homeroast mailing list Homeroasthttp://www.sweetmariascoffee.com/gallery/main.php?g2_itemIdx20">http://lists.sweetmariascoffee.com/listinfo.cgi/homeroast-sweetmariascoffee.comHomeroast community pictures -upload yours!) :http://www.sweetmariascoffee.com/gallery/main.php?g2_itemIdx20 |
| On Aug 20, 2008, at 12:32 PM, Floyd Lozano wrote: <Snip> Variacs are heavy. I suggest buying locally, if at all possible. Search on eBay, and sort by distance: nearest first search on: variac variable transformer powerstat staco pay attention to the voltage & frequency rating too. Note that there's nothing wrong with putting a 20A variac on a 15A circuit - the variac is rated at up to 20A - you just can't draw that much from the circuit; it's the device on the output of the variac that is drawing the current, not the variac itself. - allon Homeroast mailing list Homeroasthttp://www.sweetmariascoffee.com/gallery/main.php?g2_itemIdx20">http://lists.sweetmariascoffee.com/listinfo.cgi/homeroast-sweetmariascoffee.comHomeroast community pictures -upload yours!) :http://www.sweetmariascoffee.com/gallery/main.php?g2_itemIdx20 |
| You could even use a single phase of a polyphase variable transformer. It would work OK, if you disconnected the wye or delta wiring. They're just very big and very heavy. Say you have a 115v, 15a toaster/heat gun/coffee roaster ... powered through an adequate *Variac*. When you have the *Variac* set to less than 115v (stepdown), the heating device will draw proportionally lower current, and the *Variac* will draw even lower current than the heater draws, by the stepdown ratio. The variable transformer is nearly 100% efficient, the heat loss is miniscule. When set to the 115v example output, the heater is happy, *Variac * is happy and Reddy Kilowatt (house wiring and devices) is happy. If you set the transformer for 140v output, the heater will draw over 18a, and the transformer will multiply that current to over 22a draw on the power line. Your reward will be a blown breaker in the wiring panel, at best. If weak wiring was the original problem, several others might become evident at this point. The blue fire and smoke would be good places to check. Cheers, Mabuhay -RayO, aka Opa! Got Grinder? Homeroast mailing list Homeroasthttp://www.sweetmariascoffee.com/gallery/main.php?g2_itemIdx20">http://lists.sweetmariascoffee.com/listinfo.cgi/homeroast-sweetmariascoffee.comHomeroast community pictures -upload yours!) :http://www.sweetmariascoffee.com/gallery/main.php?g2_itemIdx20 |
| Another suggestion (I'm trying to do it now) instead of Variac you can buy a 1500W (or more dimmer) there are some good ones at Ebay, for what I saw, cheaper then Variac's regards Silas |
| I was able to find one at a good price, just the bare variac (well, it did come with a knob). Mount it in a box, wire a cord & plug, and you're good to go! On Thu, Aug 21, 2008 at 1:35 AM, wrote: <Snip> -- "Crime does not pay ... as well as politics." --Alfred E. Newman Homeroast mailing list Homeroasthttp://www.sweetmariascoffee.com/gallery/main.php?g2_itemIdx20">http://lists.sweetmariascoffee.com/listinfo.cgi/homeroast-sweetmariascoffee.comHomeroast community pictures -upload yours!) :http://www.sweetmariascoffee.com/gallery/main.php?g2_itemIdx20 |
| Floyd A unit which appears to be identical to the unit once sold by Tom is available at Marlin P. Jones & Assoc. Inc. Web www.mpja.com Page 6 of current catalog. Specs look the same...output 0-130 V @ 2 KVA (15A). Price is about the same. I'm posting this under the assumption that our host no longer sells this item. Josh On Thu, Aug 21, 2008 at 9:18 AM, Michael Wascher wrote: <Snip> Homeroast mailing list Homeroasthttp://www.sweetmariascoffee.com/gallery/main.php?g2_itemIdx20">http://lists.sweetmariascoffee.com/listinfo.cgi/homeroast-sweetmariascoffee.comHomeroast community pictures -upload yours!) :http://www.sweetmariascoffee.com/gallery/main.php?g2_itemIdx20 |
| The beauty of a Variac is that it can correct low voltage issues, whereas the dimmer dealie only lowers the voltage. Safe Journeys and Sweet Music Justin Marquez (CYPRESS, TX) On Thu, Aug 21, 2008 at 6:05 AM, silascoelho wrote: <Snip> Homeroast mailing list Homeroasthttp://www.sweetmariascoffee.com/gallery/main.php?g2_itemIdx20">http://lists.sweetmariascoffee.com/listinfo.cgi/homeroast-sweetmariascoffee.comHomeroast community pictures -upload yours!) :http://www.sweetmariascoffee.com/gallery/main.php?g2_itemIdx20 |
| At 04:05 AM 8/21/2008, you wrote: <Snip> Variacs can raise the voltage, Dimmers commonly only lower it. Ira Homeroast mailing list Homeroasthttp://www.sweetmariascoffee.com/gallery/main.php?g2_itemIdx20">http://lists.sweetmariascoffee.com/listinfo.cgi/homeroast-sweetmariascoffee.comHomeroast community pictures -upload yours!) :http://www.sweetmariascoffee.com/gallery/main.php?g2_itemIdx20 |
| silascoelho wrote: <Snip> Dimmers are OK for heating elements, not good for electronics, like the control circuitry of a roaster. You may luck out, but many power supplies for electronic devices expect to see something reasonably close to a sine wave. Anything involving inductance like a motor or transformer could be a disaster. Homeroast mailing list Homeroasthttp://www.sweetmariascoffee.com/gallery/main.php?g2_itemIdx20">http://lists.sweetmariascoffee.com/listinfo.cgi/homeroast-sweetmariascoffee.comHomeroast community pictures -upload yours!) :http://www.sweetmariascoffee.com/gallery/main.php?g2_itemIdx20 |
| "Anything involving inductance like a motor or transformer could be a disaster. " No argument with the first part (below), but of the motor is a universal (brush-type), it works just fine on a "dimmer". Which is a problem because slowing the fan down is kinda at crossed purpose to controlling the heat. I just last weekend split wired my Rostos to get fan and heat control--been using a variac and a router speed control to turn the heat down but was not getting the control I was hoping for. As far as ratings go, if you use a varaic in batch mode rather than continuously you can get away with an "under-sized" one. Check out the duty cycle ratings on the Superior Electric website and proceed accordingly. There have been at least a couple of discussions regarding this in the past--check the archives for miKe or Dean. Dean In da weeds. David Liguori wrote: <Snip> Homeroast mailing list Homeroasthttp://www.sweetmariascoffee.com/gallery/main.php?g2_itemIdx20">http://lists.sweetmariascoffee.com/listinfo.cgi/homeroast-sweetmariascoffee.comHomeroast community pictures -upload yours!) :http://www.sweetmariascoffee.com/gallery/main.php?g2_itemIdx20 |
| "...the dimmer dealie only lowers the voltage." The complete design using a Triac/diac dimmer would incorporate, say, a 24v boost transformer with the 0-100% T/d dimmer control at the input. With the fixed boost transformer, the dimmer gains a lot of utility with high efficiency. Cheers, Mabuhay -RayO, aka Opa! Eschew Partial Designs Homeroast mailing list Homeroasthttp://www.sweetmariascoffee.com/gallery/main.php?g2_itemIdx20">http://lists.sweetmariascoffee.com/listinfo.cgi/homeroast-sweetmariascoffee.comHomeroast community pictures -upload yours!) :http://www.sweetmariascoffee.com/gallery/main.php?g2_itemIdx20 |
| " instead of Variac you can buy a 1500W (or more dimmer) there are some good ones at Ebay, for what I saw, cheaper then Variac's" "Dimmers are OK for heating elements, not good for electronics, like the control circuitry of a roaster." "You may luck out, but many power supplies for electronic devices expect to see something reasonably close to a sine wave." Then all of the Switch Mode power supplies are just so much junk? I doubt if they care what is coming in, only the capacitor potential at the output. If some sap design needed a sine wave input, a 1:1 input transformer, with a tertiary winding at parallel resonance with a capacitor would do it. Some have gone overboard and rectified any and all incoming garbage to supply an HF power oscillator driving another resonant circuit at 10 - 100 khz. You can get all the perfect sine waves and power you want. "Anything involving inductance like a motor or transformer could be a disaster." Does that mean all of the variable speed drill motors don't really work, just an illusion? Mmmm- all these tools that only appear to work properly- sure fooled me. Don't believe everything you hear. Cheers, Mabuhay -RayO, aka Opa! -- "When the theme hits the bass, I dance the Jig!" - -Virgil Fox at the Mighty Wichita (ex- NYC Paramount) WurliTzer- 1976 Homeroast mailing list Homeroasthttp://www.sweetmariascoffee.com/gallery/main.php?g2_itemIdx20">http://lists.sweetmariascoffee.com/listinfo.cgi/homeroast-sweetmariascoffee.comHomeroast community pictures -upload yours!) :http://www.sweetmariascoffee.com/gallery/main.php?g2_itemIdx20 |
| David that is right, my intention is to use that with my Popper heater only (I have small trafo 12Vx1A for the dc motor) . Unless the electronic device that will be connect to the variac is isolated by a transformer + linear power supply, and doesn't use the line frequency as reference (zero cross detection and similar) the variac really cannot be used. For heater, no issues at all Silas |