hinekadon (03-11-18)
Just check that sensor wiring and the power for the pump are kept physically far enough apart. Maybe rodents chewed through the insulation.
Other than that I can only imagine a secondary (very minor) lightning strike on the roof somehow finding it's path through the sensor wiring
Last edited by Uncle Fester; 03-11-18 at 12:01 PM.
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hinekadon (03-11-18)
it appears to me that the pool and roof are commoned on one side ? ps some thanks for those wouldnt go astray ! cheers don
edit: just had a looky at the b/d on the right there are same two circuits that go to the sensors . as a result the transistor is balanced between on and off thru bias of q2 and held in place by the other transistor , so the difference between the roof sensor or the pool sensor is commoned back to q2 and set by the pot so as to operate the relay thru collector of q2.
Last edited by hinekadon; 03-11-18 at 05:59 PM. Reason: more
RedXT (08-11-18)
Mains across any semiconductor device that's not rated for it tends to produce an immediate explosion, usually resulting in blowing
the device to bits, often only leaving the remains of the legs behind or part of the body.
This thing has had a slow burn, in other words it's got really, really hot - so much so the plastic has slow melted.
It's not something I had seen much at all in my 45 years of electronickery.
RedXT (08-11-18)
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Well so far so good, as I mentioned earlier there was a possible short in the roof sensor so I carefully cut into the brass end and separated the wires and it tested ok.
I then replaced the transistor ( everything else looked ok)
Its now running normally, started the pump as it should, just need a hot day to test it further. Its only been running for about an hour so fingers crossed !!
Thanks again everyone for you're help.
cheerrs thomo
Last edited by RedXT; 08-11-18 at 12:20 PM.
you can test it by holding a cig lighter on the other probe and see if it changes over, for a short time
RedXT (09-11-18)
hinekadon (09-11-18)
Still seems to be a problem with the roof sensor, the controller sometimes waits for a signal from the roof sensor and wont start sometimes it comes straight on.
Once I wiggled the sensor end and the unit clicked and started working. Could this blow the circuit again.
If I disconnect it the unit wont start
Can I bypass the roof sensor or is there a cheap new one available
Dont know if this would work
But it aint cheap
thanks thomo
all we have to do is find out what sort of sensor it is they are only a couple of bucks if you know could be a pt 100 which has temp /ohms of 25 degrees equals 100 ohms or some thing like that so put a ohmmeter across it and see disconnect it first of course , could be ntc or ptc type also cheers don
RedXT (13-12-18),Uncle Fester (12-12-18)
No they are specific for a certain model.
You need to measure how many ohms it has at around 25˚C like Hinekadon said.
I am assuming it has an intermittent conctact so wiggle it until you get a reading. I assume it will be between 100Ω and 10k, so anything showing in the MΩ range or less than 1Ω is faulty.
You do that in the evening when the sun is down.
Then you warm it up with your hand or pour a cup of hot water over it.
Then you measure again.
If the Ohm value is lower it is an NTC, if higher a PTC.
I am tipping an NTC, hopefully. If PTC things will be tricky as there are non linear types and the one you need can be hard to find.
Jaycar has all the standard NTC values, choose the one that is closest to what you measured before you heated it. Doesn't have to be perfect, you have an adjuster on the PCB.
Cut off the faulty one(taking about 10cm of the wire with it, that could be the actual fault not just the sensor itself) and solder on the new one. Dip it completely in Araldite. Let it harden and dip it again in fresh Araldite.
Put a bit of heatshrink tube around it.
All done for $1,95 (assuming you already have Araldite and heatshrink tube lying around)
Last edited by Uncle Fester; 12-12-18 at 08:02 PM.
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At 26C it reads 1.834k and at 46c it reads 2.220k so I guess its PTC unfortunately
Anything I can try
Are you 100% sure? That is bad. None of the stores I am aware of have this. Element14 (Farnell) I keep getting access denied.
A few things:
Ditch the controller, connect the pump to a GPO and switch manually.
Toughen up and swim in cold water like me In summer my pool is still very warm.
Try grinding VERY CAREFULLY away the resin or what ever the sensor is encapsulated in at the point where the wire goes in to expose the copper and re-solder it, but try bending the wire nearby first. Maybe there is a break further back
Program a 1$ PIC micro (12F683) and build your own controller using an NTC.
Contact Heatseeker and ask if you have to sell a kidney or not to afford a replacement sensor.
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I drink like a fish but dont swim much myself, its for the wife and grankids
I did carefully cut the metal end of the sensor and thought I fixed the short then used hot melt glue gun to reseal it then heat sinked over the top but obviously didn't do a good enough job. (no breaks)
Heatseeker dont support this any more.
I,ll slip it back into the rubber tube on the roof and see what happens, Its just handy to turn the pump off when it gets to 28°
Thanks again for the help
cheers thomo
Last edited by RedXT; 13-12-18 at 01:52 PM.
Last edited by Uncle Fester; 13-12-18 at 04:32 PM.
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hinekadon (13-12-18)
nope thing just dont add up the difference is not believable for ntc or ptc i suspect its a pt100 thats full of water and corroded to get that sort of results just solder a 100 ohm resister across the wires and see what happens if it is pt100 it will work to some extent but dont expect any accuracy just to see if it is ???? and get back to us cheers don
when youve done the solder job dunk the whole thing in enamel paint and wait for it to dry i mean wires and all
Last edited by hinekadon; 13-12-18 at 06:09 PM. Reason: more
RedXT (14-12-18),Uncle Fester (13-12-18)
Don, I doubt it is a PT100.
They are used for accurate temperature measurements in a wide range using a bridge and a differential amplifier because the change of resistance is very low compared to standard NTCs.
This circuit just had a simple transistor for the input. I don't remember seeing any OP amp IC. The images are gone.
The variation of the resistance fits roughly for a 2k NTC if it were the other way around, although it could be even higher.
h8fg4 you said that it worked but it had an intermittent short.
Still it might be a good idea to run a test using a pot instead of the sensor and find out at which values it switches on and off because an internally corroded sensor could be producing random values. That way we can really confirm if it is a PTC.
I suggest a 4k7/5k pot though*
Also a bit confused that you want the pump to switch OFF at 28˚. Do you mean the pool water or the roof sensor?
Are there two sensors, one for the pool water and one for the solar heater? I understand the one we are talking about is for the roof to switch the pump ON.
Using hot glue is a bad idea to insulate a solar sensor. That is why I suggested Araldite.
* Another idea is to also measure the voltage across the sensor input just when the motor switches on with the pot.
Lets assume the motor just switches on when the pot has a value of 2kΩ and you measure 0.7V across it.
Grab another pnp transistor and use 2k2 as the emitter resistor across the input. The collector of this transitor using a resistor of 2k2 to the negative of the capacitor with the blue resistor on the shown image posted below.
Now you can use pretty much any old NTC from Jaycar, I suggest 10k and connect it to base and +, NOT ground!
Then solder a 10k trim-pot between the base and ground and adjust until you get 0.7V over the emitter resistor.
You have now inverted the function of the sensor input. If the NTC gets lower the voltage on the input will get higher.
If you want to do this I will draw something up sometime tomorrow, getting late now.
Last edited by Uncle Fester; 13-12-18 at 11:40 PM.
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hinekadon (13-12-18)
heres the circuit bd post 5
Uncle Fester (13-12-18)
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Quote : Also a bit confused that you want the pump to switch OFF at 28˚. Do you mean the pool water or the roof sensor?
Are there two sensors, one for the pool water and one for the solar heater? I understand the one we are talking about is for the roof to switch the pump ON.
there are 2 sensors pool and roof when I go to work I turn it on and during the day it starts if pool temp is under 28 but turns off when it gets 28 otherwise it could
be 32 by the time I get home.
Quote* Another idea is to also measure the voltage across the sensor input just when the motor switches on with the pot.
Lets assume the motor just switches on when the pot has a value of 2kΩ and you measure 0.7V across it.
Grab another pnp transistor and use 2k2 as the emitter resistor across the input. The collector of this transitor using a resistor of 2k2 to the negative of the capacitor with the blue resistor on the shown image posted below.
Now you can use pretty much any old NTC from Jaycar, I suggest 10k and connect it to base and +, NOT ground!
Then solder a 10k trim-pot between the base and ground and adjust until you get 0.7V over the emitter resistor.
You have now inverted the function of the sensor input. If the NTC gets lower the voltage on the input will get higher.
Sorry mate remember u are talking to a retired mechanic, most of this stuff goes straight over my head
When I did the measurement I dropped the end in a cup of water that was 50c , I will try it again using a lighter perhaps
thanks
h8 dont worry about your lack of knowledge thats what we are here for its a question and answer site so even the silliest are answered so long as we are not getting jerked off we are happy to extend our minds even if they are old and a little forgetful results are what counts you should have realised that , please dont let it go over your head ,just ask and be honest we dont think of anyone as stupid by the questions . we manage to take a broad mind to problems dont be frightened to have a try to build your fault away to save a buck or two as we have all done it nomeat said he would modify his circuit so wait for him no worries ???
Uncle Fester (14-12-18)
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