How to size a potentiometer?

[bennihana]

I would like to add an analog control to by boil kettle element but i have never had to deal with potentiometers in my career before. How do i size a potentiometer and figure out what i need. I run on a 230v systerm and have a 2000w element that i would like to be able to turn down the power on incase of impending boil overs and to control the boil off rate a little better. Also i dont know if this is needed or not but im on a 50mhz cycle. Can anyone help?

 

[stlbeer]

It's been done already. Here's a solution for $22.50 plus shipping.

http://www.auberins.com/index.php?main_page=product_info&cPath=2_30&products_id=332

 

[Brumateur]

I'd rather buy this kit - http://www.ebay.com/itm/1pc-KYOTTO-AC-Solid-State-Relay-SSR-KR2040AX-280VAC-40A-/140553987088
It's 40A rated and cheaper.

 

[brew_ny]

or something like this

http://www.ebay.com/itm/251364375914?_trksid=p2055119.m1438.l2649&ssPageName=STRK:MEBIDX:IT


S_M

all the best

 

[Brumateur]

This dimmer will work, but it's highly recommended to install a fan or bigger heatsink. Otherwise risk of overheating is too high.

 

[bennihana]

The kyotto seems to be the item i am looking for. half price from the auber and still cheap with the shipping. seeing as how i need two of them it will work just fine i think.

 

[bennihana]

I have found that i can buy the components seperately for cheaper on ebay and for free shipping. So if the kyotto in the picture has a 2W 500Kohm potentiometer can i use one of the same wattage but different ohms. or can i use one that has a higher ohm rating.

 

[Brumateur]

Optimal resistance for 240V is 470K-500K. Youcan higher value but this way only part of rotation diapason will be in use.

 

[atoughram]

diapason

di·a·pa·son
ˌdīəˈpāzən,-sən/Submit
noun
noun: diapason; plural noun: diapasons; noun: open diapason; plural noun: open diapasons; noun: stopped diapason; plural noun: stopped diapasons
1. an organ stop sounding a main register of flue pipes, typically of eight-foot pitch.
2. a grand swelling burst of harmony.
3. literary the entire compass, range, or scope of something.

Sorry - I had to look that one up... now back to your regularly scheduled programming.

 

[Brumateur]

range

 

[bennihana]

this has to be used along with a regular SSR right? you cant substitue this setup for a regular SSR correct?

 

[atoughram]

this has to be used along with a regular SSR right? you cant substitue this setup for a regular SSR correct?

No, You dont have to have a 2nd SSR although it is good to have some sort of disconnecting device such at a two pole switch or contactor upstream of the SSVR.

 

[bennihana]

No, You dont have to have a 2nd SSR although it is good to have some sort of disconnecting device such at a two pole switch or contactor upstream of the SSVR.

ok good, so where do i put my leads from my PID? do they just go on the terminals of the ssver along with the potentiometer?

 

[atoughram]

I only use a SSVR on the boil kettle - no PID at all. Not sure if you can have both at the same time.

 

[brew_ny]

I only use a SSVR on the boil kettle - no PID at all. Not sure if you can have both at the same time.

you can use a PID if it does relay output, which it acts like an on/off switch but you still need the potentiometer or I believe you can add a resistor

I have a couple of PIDs that are relay output only and have used them with SSVRs

worked pretty good but it is easier just to use the dial

all the best

S_M

 

[k_mcarthur]

Main problem I had sizing a pot wasn't the resistance but the required current. My ssvr was rated at 2w but most pots are only .25w. Kept burning them until I figured that out.

 

[bennihana]

Would and SCR be a better solution?

 

[Jawbox0]

So I've got a dumb question, can a single potentiometer control two different relays?

I've got two 120v elements on two different 120v circuits and it simplify my controls if they ran off a single potentiometer, though not absolutely necessary.

 

[Brumateur]

SSVR circuitry doesn't allow to use same pot for two SSVR. But two or more pots can be mechanically combined in one unit.
Like this one - http://www.ebay.com/itm/2W-220K-ohm-4-Terminals-Rotary-Carbon-Film-Potentiometer-Pot-/310753176894

Actually its a triple pot and you need only double one . Try to search yourself. You can probably find a cheaper deal.

 

[mattd2]

ok good, so where do i put my leads from my PID? do they just go on the terminals of the ssver along with the potentiometer?

What PID controller do you have? As most (not all) already have a manual function to set the strength of the boil.
My suggestion if you are looking at getting the SSVR, is to buy the kit with everything you need supplied. That way you know you will get all the parts you need and not the wrong type (e.g. SSR vs. SSVR).

 

[bennihana]

What PID controller do you have? As most (not all) already have a manual function to set the strength of the boil.
My suggestion if you are looking at getting the SSVR, is to buy the kit with everything you need supplied. That way you know you will get all the parts you need and not the wrong type (e.g. SSR vs. SSVR).

I purchased one of Aubers PIDs with an ssr output and it does have a manual mode but I just wanted a knob so that I could quickly dial down the current in case of boil overs or something like that. I wound up piecing together some ssvr's from ebay and some POTS from ebay as well. I go the exact same sizes as the one Aubers offers for less that half the price I think.

 

[P-J]

What PID controller do you have? As most (not all) already have a manual function to set the strength of the boil.
My suggestion if you are looking at getting the SSVR, is to buy the kit with everything you need supplied. That way you know you will get all the parts you need and not the wrong type (e.g. SSR vs. SSVR).

For those interested, here is a diagram showing the SSVR set up that is from Auber Instruments:

As always click on the image to see and save a fullscale diagram for your build.



I hope this helps those looking for ideas.

P-J

 

[kevreh]

Thanks for adding that P-J.

I'd rather buy this kit - http://www.ebay.com/itm/1pc-KYOTTO-AC-Solid-State-Relay-SSR-KR2040AX-280VAC-40A-/140553987088
It's 40A rated and cheaper.

Yeah, but will it last? Too cheap to be any good? Anyone been using these?