PWM for Boil Kettle Control

I used a 10uf electrolytic capacitor and soldered it in, so I will see if it works. After I did more looking I suppose I needed a 20uf capacitor. I have a couple more days waiting for the proverbial slow boat from China before I will know though..

Well, I'm bummed.. My package from China showed up with the heat sinks and SSR's so I was excited and wired it into my PWM to see how it worked. No joy. As soon as I kicked on the 230v power it ran full power no matter the setting on the PWM with the 10uf capacitor.
Does anyone know if a 20uf would work better? I have power to the ssr as the led lights up. Before I added the 10uf capacitor the PWM worked with a little elec motor out of an RC car. Now it runs the motor from the RC car WFO and the SSR appears to be in the same state.
This isn't what I was hoping for....

Did you get the polarity right when you soldered the capacitor in place? Polarity matters with electrolytic capacitors.

freddyb said:

Did you get the polarity right when you soldered the capacitor in place? Polarity matters with electrolytic capacitors.

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Oh! I did not know that. I will go resolder it the other way. I hope I didn't wreck it. I thought it just went from one leg to the other through the magic voodoo inside.

FreddyB, YOU ROCK!! I am Happy now! I can turn the PWM up down and all around! This will be fun now, I won't have to babysit the boil kettle anymore. Thanks FreddyB!

freddyb said:

I used a PWM kit from Bakatronics #FK804, cost $8, and swapped a capacitor to reduce the cycle time to 1Hz (also calculated the cap value for 1/2 Hz but deemed it unnecessarily slow). Hooked the output directly to the SSR and it worked great in my new 5500W brew kettle.

My understanding of SSRs is that the faster you cycle them, the hotter they run. That and how much current they're handling.

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This question may have been asked but, all I have to do with the Bakatronics #FK804 kit is replace the kits C1 cap with a 2.2uF cap and everything should work fine? Nothing else needs to be modified on the FK804 circuit board?
Thanks

SpottedDogBrewing said:

This question may have been asked but, all I have to do with the Bakatronics #FK804 kit is replace the kits C1 cap with a 2.2uF cap and everything should work fine? Nothing else needs to be modified on the FK804 circuit board?
Thanks

Click to expand...

Correct.

freddyb said:

Correct.

Click to expand...

Sweet!! Thanks for the quick response

freddyb said:

I use a 2.2uF cap and it works great, around 1 second cycle time. I recall finding an error (or typo) with the calculations provided with the kit but I don't recall exactly what it was.

I've done quite a few batches using this system and I absolutely love it. Very "responsive" with my 5.5kW element, even with a full 13.5 gallons in the BK. I can go from rolling boil to gentle boil and back to rolling in a few seconds by adjusting the potentiometer. I put a big knob on there so it looks sweet too.

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According to the pic which componet do I replace with the 2.2uFcap?
:rockin:Thanks for the help
Also will I be able to desolder the cap and solder the new 2.2uF cap in?

wrench said:

In this kit, the capacitor I want to swap out is C1, correct?

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"C1 is between the ground post and the Pot! C2 is next to the 555 Chip"

This answer is straight from Bakatronics

I took a look at my board and drawings last night and it took me a small bit to figure out which was which, since "C1" was not anywhere to be found on either. But studying the schematic, which I am no expert at, finally revealed C1.

Then I come here and find the info posted for me...

freddyb said:

I use a 2.2uF cap and it works great, around 1 second cycle time. I recall finding an error (or typo) with the calculations provided with the kit but I don't recall exactly what it was.

I've done quite a few batches using this system and I absolutely love it. Very "responsive" with my 5.5kW element, even with a full 13.5 gallons in the BK. I can go from rolling boil to gentle boil and back to rolling in a few seconds by adjusting the potentiometer. I put a big knob on there so it looks sweet too.

Click to expand...

Do you think I could use this capacitor from mouser?
647-UVR1C330MDD1TD
Nichicon Aluminum Electrolytic Capacitors - Leaded
33uF 16V 85c
US HTS: 8532.22.0020 ECCN:EAR99 COO:JP

This is what I bought! Is this correct?

That should work. I used part # 272-997 2.2µF 50V 20% Nonpolarized Electrolytic Capacitor 9,000Hz.

tsisson said:

That should work. I used part # 272-997 2.2µF 50V 20% Nonpolarized Electrolytic Capacitor 9,000Hz.

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Now does it matter which way it gets soldered in? Is there a way in or way out!!

If it's non-polarized then it doesn't matter. I couldn't quite tell from your picture what the part number was. From the picture it looks similar to mine with no white band around one end and both ends having the groove around them. If there is no printing on it indicating polarity you should be fine. If it is polarized you will need to determine which way it goes in.

http://www.bakatronics.com/shop/item.aspx?itemid=383

http://cgi.ebay.com/DC-Motor-Speed-...501?pt=LH_DefaultDomain_0&hash=item20b88bf155

These two looks identical. the Ebay description says the duty cycle of only 0-92.5% , not full range.

Sorry if this is a dumb question, but the 5500W element will take draw more than 15 amps, and the FK804 says:

"see our MX033 and MX066 for 30 amp capacity"

I see a lot of people here saying that they used the FK804 and a 5500W element. Do I need the larger capacity PWM or is the FK804 definitely fine?

freddyb said:

I used a PWM kit from Bakatronics #FK804, cost $8, and swapped a capacitor to reduce the cycle time to 1Hz (also calculated the cap value for 1/2 Hz but deemed it unnecessarily slow). Hooked the output directly to the SSR and it worked great in my new 5500W brew kettle.

My understanding of SSRs is that the faster you cycle them, the hotter they run. That and how much current they're handling.

Click to expand...

disclaimer: I am not an electrician - just a DIY guy with some tech fun.

SSRs are triggered by the PWM unit. The voltage and amperage you switch with the SSR is independent from the low-voltage side (trigger).
Meaning the pulse from the PWM, i.e. on 5V and a few milli-amps, should be fine. One thing to consider is the pulse setting as noted about with the capacitors. does this make sense?

Perfect, thanks - makes sense. Talked through it with my wife's cousin who is an electrician and he did finally get what I'm trying to do.

BayerischBier said:

disclaimer: I am not an electrician - just a DIY guy with some tech fun.

SSRs are triggered by the PWM unit. The voltage and amperage you switch with the SSR is independent from the low-voltage side (trigger).
Meaning the pulse from the PWM, i.e. on 5V and a few milli-amps, should be fine. One thing to consider is the pulse setting as noted about with the capacitors. does this make sense?

Click to expand...

What do you think of this:
PWM Motor Speed Control Reversible Switch Regulator DC 6V 12V 24V 3A Governor.

http://www.wish.com/c/55bc3c8eb5c50155de61dc71

Will it work to control a small 12v pump or 5500w Heating element?

I hate to be that guy who revives an old thread, but I had some questions about how these things work, specifically for AC current.
Everywhere I've read says you can't PWM an AC circuit, let alone an inductive heating element. Obviously that isn't true as you're all doing it - so I want to understand exactly how they work, before settling on a wasteful Solid State Voltage Regulator (SSVR) to 'trim' the voltage.

So from my understanding, once the board is modified to PWM at 1Hz (swapping the capacitor), the potentiometer is used to adjust the Hz of the signal which can be calculated by using that formula shared by interplexr.

—————————————————————————
Charging Time - T1 = 0.693(Ra+Rb1)C
Discharge Time - T2 = 0.693(Rb2)C
Frequency - f = 1/(T1+T2)

If you're using the circuit above, Ra and Rb are both 1k ohm resistors.

Rb1 = 1k + one side of 1M pot depending on where it's position is

Rb2 = 1k + other side of 1M pot depending on where it's position is

Pot all the way to one side: Rb1 - 1k ohm and Rb2 - 1M ohm

Pot in the middle: Rb1 - 501k ohm and Rb2 - 501k ohm
—————————————————————————

A few questions then:

How does the above equation work?
- The pot when turned fully 'on' should give no resistance so it's just the 'Ra' 1k resistor + 'Rb1' 1k resistor that creates the Hz output.
Charging time: T1 = 0.693(1000+1000)C = 1386C. What is C?

- Does this mean that the PWM cannot ever be 'fully on', and that you will always be pulsing the SSR/heating element?

- How does the 'Pot in the middle' bit calculate?
Rb1 - 500k would = 1000 - 500,000 which is negative resistance?

How does switching the AC work?
- Is the key to this working for AC, in using a zero-crossing Solid State Relay so that it doesn't really matter how the PWM Hz doesn't match/align to the input voltage Hz? E.g. if you end up with a .31Hz PWM signal, that's a duty cycle every 3.2258 seconds. in NZ our AC is 50Hz so does that mean the AC will alternate [50 * 3.2258 = 161.29] 162 times as the zero-crossing will allow the signal to both start at 0 and finish at 0?

Can someone tell me the functional switching potential from the device? E.g. the fastest and slowest switching available?

Thanks for any and all help.