Variable resistance SSR for boil control?

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WPStrassburg

WPStrassburg

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Would this work as a boil control? Do you need a voltage to the pot or relay or does the relay sense the resistance of the pot?
What would the cycle time be? Is the 47 to 70 Hz the input power range? Cheap boil control would be nice!

http://www.ebay.com/itm/1pc-KYOTTO-...088?pt=LH_DefaultDomain_0&hash=item20b9aba410

http://www.kyotto.com/PDF/PDF/KR2010AX.pdf

$(KGrHqZ,!p!E8VkrBh00BPN5rdEdG!~~60_57.JPG


KYOTTO AC Solid State Variable Relay

SSR

Part No. : KR2040AX

AC Load out : 24-280VAC 47-70Hz 40A

Resistance control in : 0-500KΩ

CE safety

1 set = SSR + φ24mm 500KΩ B type potentiometer

+ 0-100% soft plastic panel (with glue)

made by KYOTTO, in Taiwan

dimension : 58.0x44.0x22.0mm, LxWxH

Scwer type In Out terminal

Net weight approx : 117g, 1 set

Each bidding lot is for 1 set

N290 0.65 28 20111007+60g+20g
 
I think that if you used the pot as you have it shown, you'll just have a point below which the SSR will be "open" and a point on the dial above which it will be "closed", just a switch without any control. The SSR is just a switch. It is either open or closed, it's not like a faucet that has a "half way open" setting. Control over your boil is achieved by the percentage of the time the element is on. I.E., on a 5 second system, 20% would be 1 second on, 4 seconds off. 70% would be 3.5 seconds on, 1.5 seconds off.

The cheap route that some are using to achieve what you are trying to do us to use this PWM with a minor modification in conjunction with the SSR. Check out this thread as well.
 
A SSR is always on or off - think of it as a light switch. So if you want 50% heat it has to switch on and off, on and off continuously with it being on 50% of the time. That's what a PWM controller does.
 
I understand the function of the ssr and pmw, but this is switching the ssr on/off on what seems to be a resistance signal. How I don't know though. What are the chances that this ssr already has the pmw signal built into it and just has the pot to adjust the on time?
 
I know some who use one like that. It should work like a pwm, it uses the load power for the control circuitry somehow. I don't think it uses zero volt switching.
 
WPStrassburg said:
I understand the function of the ssr and pmw, but this is switching the ssr on/off on what seems to be a resistance signal. How I don't know though. What are the chances that this ssr already has the pmw signal built into it and just has the pot to adjust the on time?
Click to expand...

You can make a zero crossing SSR act like a light dimmer but it's going to take a lot more than a potentiometer to make it work. You will need the potentiometer, a diode bridge network and a couple of resistors to divide the line voltage down to the range the SSR is designed to switch at. But the adjustment will be non-linear.

Also, you will be switching the element on & off at 120 times a second but I don't know if this matters.
 
Interesting find! After looking through the spec sheet, I think it will work as you intend it to. Regular SSR's use a small control voltage to control the output but this one apparently has enough other circuitry built in to allow an external pot to adjust the output. For no more than it costs, I'd say it's worth a try! Please report back on your findings if you do - this may be a simple, effective solution.
 
These have just recently started showing up as sellers understood what we are using them for. I would still pay a little extra for zero crossing.
 
Has anyone seen where it says zero crossing or not? I haven't seen a definate one way or the other, but would prefer teh zero crossing as well. One of the sites with them listed mentions zero crossing or random as an option, but doesn't say what indicated one vs the other.
 
Since the spec sheet mentions adding a filter capacitor to reduce EMI & doesn't mention zero-crossing, I suspect it's switching anywhere along the waveform. The block diagram isn't much help....
 
NoCornOrRice said:
that is amazing, I have never seen a pot-driven SSR before. WOW. too bad I just ordered from Auber. I wonder if that really works?
Click to expand...

Crydom has been selling them forever. They are called proportional control SSRs or something similar. They are very expensive, but very convenient because the analog to PWM is internal. Just add pot. Search ebay, I've seen them there.

[edit] here's one at digikey. I use this Crydom relay (2425) but not the PCV version.

http://parts.digikey.com/1/parts/758103-power-control-ssr-25a-dc-10pcv2425.html
 
No! This will not work. A Pot just varies voltage and current. A SSR uses a triggering voltage on the signal terminals to electronically open and close the circuit on the load terminals. You have to supply a certain voltage to the signal terminals to get the SSR to operate. Applying higher or lower voltage to the signal terminals will not vary the voltage or current delivered through the SSR load circuit.

In addition, you have to have an external power supply for the SSR signal circuit. Some SSR's use AC current and some use DC current. Its almost always low voltage for the signal circuit.
 
mabrungard said:
No! This will not work. A Pot just varies voltage and current. A SSR uses a triggering voltage on the signal terminals to electronically open and close the circuit on the load terminals. You have to supply a certain voltage to the signal terminals to get the SSR to operate. Applying higher or lower voltage to the signal terminals will not vary the voltage or current delivered through the SSR load circuit.

In addition, you have to have an external power supply for the SSR signal circuit. Some SSR's use AC current and some use DC current. Its almost always low voltage for the signal circuit.
Click to expand...

Ah, but what if the SSR has an voltage-to-frequency (PWM) generator internally? This is the case.

I posted this sometime in the past. It's the output duty cycle vs the DC input voltage (from the pot). From the datasheet for a Crydom proportional controller (SSR). See this: http://www.crydom.com/en/Products/Catalog/p_cv.pdf
2011-11-02_093020.jpg
 
I looked at the specs for this part and from what I see it can't have a internal PWM. Instead it's using the control voltage to set when after zero crossing the SCR turns on. This is why the curve is shaped the way it is.

You won't be able to control this part with just a potentiometer because a potentiometer supplies no voltage and you still need a outside voltage source. BUT you could control the part with a DC powers supply and a potentiometer.

I attached a drawing of one way you could control one of these.

Variable SSR Control.jpg
 
This is a completely different part than the one passedpawn was referencing. The control circuit I drew was for the part he referenced.

This one can be controlled with a potentiometer but since it seems this part is not available through distrubution it does not matter.
 
The OP did post a source for the unit he had a question about. Its spec sheet shows a UJT (Unijunction Transistor) in the block diagram. These devices are typically configured as relaxation oscillators that use a pot to adjust the frequency. I suspect that's how the pot that's supplied is used and the spec sheet shows a resistance as a control input vs a DC or AC input voltage shown on the majority of SSR specs. This leads me to believe its internal input circuitry is a bit different.
 
thargrav said:
I looked at the specs for this part and from what I see it can't have a internal PWM. Instead it's using the control voltage to set when after zero crossing the SCR turns on. This is why the curve is shaped the way it is.
Click to expand...
Oh man, you're right, that's why it looks sort of sinusoidal :drunk:

You won't be able to control this part with just a potentiometer because a potentiometer supplies no voltage and you still need a outside voltage source.
Click to expand...


You don't need the external DC supply with the LPCV series. It has a 12VDC output on one of the pins. $$$
 
Junkster said:
The OP did post a source for the unit he had a question about. Its spec sheet shows a UJT (Unijunction Transistor) in the block diagram. These devices are typically configured as relaxation oscillators that use a pot to adjust the frequency. I suspect that's how the pot that's supplied is used and the spec sheet shows a resistance as a control input vs a DC or AC input voltage shown on the majority of SSR specs. This leads me to believe its internal input circuitry is a bit different.
Click to expand...

Please share.
 
Junkster said:
The OP did post a source for the unit he had a question about. Its spec sheet shows a UJT (Unijunction Transistor) in the block diagram. These devices are typically configured as relaxation oscillators that use a pot to adjust the frequency. I suspect that's how the pot that's supplied is used and the spec sheet shows a resistance as a control input vs a DC or AC input voltage shown on the majority of SSR specs. This leads me to believe its internal input circuitry is a bit different.
Click to expand...

So UJT is actually something real... never thought to Google and wiki now only has me slightly less confused. Sounds like 555 timers were an improvement for timer operations, but wiki still mentions ujt as part of some triac & ssr control circuits.

Does the UJT circuit provide the same control as a pmw would or does it just temporarily kill the input signal? Is the cycle timing based on the pot resistance and therefore non zero crossing or is the zero crossing in the triac circuit?

Here's the circuit for the ssr & pot from the Kyotto site.
kr_03.jpg
 
Yeah, I'm thinking it's built in. I don't know if it's like a true PWM or not - I wish it was a little more clear in the description. Some SSR's DO show zero-crossing circuit in their block diagram, I don't know ft this one has it - I doubt it. Maybe a full-blown description in Chinese explains it, but I couldn't find much in engrish.... <G> There is some contact info on their webpage & it may be worth a try to get your questions answered via that route.
 
WPStrassburg said:
So UJT is actually something real... never thought to Google and wiki now only has me slightly less confused. Sounds like 555 timers were an improvement for timer operations, but wiki still mentions ujt as part of some triac & ssr control circuits.

Does the UJT circuit provide the same control as a pmw would or does it just temporarily kill the input signal? Is the cycle timing based on the pot resistance and therefore non zero crossing or is the zero crossing in the triac circuit?

Here's the circuit for the ssr & pot from the Kyotto site.
kr_03.jpg
Click to expand...

UJT's don't work the same as a PWM. The circuit starts off every time the voltage crosses zero, wcich is 120 times a second then it turns on depending on where the resistor is set. It's non-linear with the most sensitive settings in the center of the range.
 
I emailed Kyotto and recieved this response this morning

Hi Walter,

KR2040AX isn't a zero or ramdom relay, it's phase control switching type.
Please see attached file.

Best regards,

-------------------------------------------------------------------
Deena Tseng
Secretary
KYTECH ELECTRONICS, LTD
No. 68, Lane 131, Sec 4, Fudan Rd.,
Pingjhen City, Taoyuan County, Taiwan, R.O.C.
TEL: 886-3-4930055
FAX: 886-3-4922455
E-mail: [email protected]
Http://www.kyotto.com
-----------------------------------------------------------------

----- Original Message -----
From: Walter Strassburg
To: [email protected]
Sent: Wednesday, March 07, 2012 2:16 AM
Subject: KR2040AX


Hello,
Is the KR2040AX SSR a zero or ramdom crossing relay? Do you have a detailed specification sheet available for it?
Thank you,
Walter

​
[FONT=&#26032;&#32048;&#26126;&#39636;][/FONT]
[FONT=&#26032;&#32048;&#26126;&#39636;][/FONT]The file that was attached was the same as the pdf I posted in the orignal link.

So what is phase control?
 
rummaged through that thread and they are using a Newark PSR-25 for $47.74
http://www.newark.com/jsp/search/productdetail.jsp?SKU=97K7822&CMP=AFC-GB100000001

It linked to a 68 page thread..
http://homedistiller.org/forum/viewtopic.php?f=2&t=3342&start=1005

And recently one of the guys said:
"I just got a newark code for 15% off after my recent order and they said it can be shared with friends. It is "NEW2P" and expires March 31st"

so now it is just over $40, which is pretty sweet....

Passedpawn, I have to make an order for some other stuff and may get one of these just to play with... if you want to borrow to test, you are welcome...
 
clearwaterbrewer said:
rummaged through that thread and they are using a Newark PSR-25 for $47.74
http://www.newark.com/jsp/search/productdetail.jsp?SKU=97K7822&CMP=AFC-GB100000001

It linked to a 68 page thread..
http://homedistiller.org/forum/viewtopic.php?f=2&t=3342&start=1005

And recently one of the guys said:
"I just got a newark code for 15% off after my recent order and they said it can be shared with friends. It is "NEW2P" and expires March 31st"

so now it is just over $40, which is pretty sweet....

Passedpawn, I have to make an order for some other stuff and may get one of these just to play with... if you want to borrow to test, you are welcome...
Click to expand...

Absolutely! If you need to borrow any equipment, I have extras scopes & stuff. I'd love to look at the output waveform.
 

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