I have similar reservations about it. Typically you don't water cool. Resist your elements until 15kw+ but I'm just messing around here. It's really more of a size trade-off.
@@Telukin An RCBO or GFCI wouldn't trip if the fault happens after the automotive transformer. And at least for these types of tests, I doubt much would change if DC was used instead of AC.
You know, instead of that big complicated driver circuit for over-temperature protection, you could just use a couple of bimetallic temperature switches in line with the resistor instead. (That is how this sort of thing would typically be protected in any real-world product anyway) Also note that if your water is actually in contact with the leads of the resistors (which it will be unless you've been very careful with sealing them all off), then the total resistance of the apparatus can theoretically change depending on the mineral content (hardness) of the water you are using. You can also potentially get some leakage current between your voltage source and ground (which would, for example, cause problems for GFCI devices, etc).
This is all very true. I did attempt to seal the resistor pack but I would not rely on that for a long operation. My water here is about 1.5M ohm / in. Although I think I'm going to use this heater For a heated patio or driveway when it snows. We will see. I did ground the chassis. And it does not work with GFI outlets haha.
the continuous flow heater has already been invented. In Germany three resistors each at 230V AC, three phases 400V. The pipe is grounded and it doesn't matter.
How to upset your girlfriend. Ah, who am I kidding? We both know there's no girlfriend. Sorry bro. I only lash out to hide my own shame. Cool resistor, man.
I think that using the voltage and current is probably the most accurate way to measure the power since your resistor changes with temp. You could also plug a kilowatt power meter (240V version ofc) on the output of your variac and get a power measurement there. You want to do it on the output of the variac instead of the input because the variac is not 100% efficient. So placing it on the variac output gets rid of that power loss from the measurement.
I could also put a fixed amount of water in it and run it for a fixed amount of time in a thermal Anechoic chamber… If accounting for the change in fixture temperature the change in water temperature could tell us the exact power input. what fun.
Good grief man, just get a wire wound ceramic resistor. They're made to go over pipes for cooling. Come to think of it, power resistors are actually pretty easy to make. All you need is nichrome wire and ceramic tube, cover the whole thing in glaze once you get the resistance right, fire it and you're done. Your gap between the resistors and the pipe isn't helping your heat transmission any. Fill it with sand.
An unnecessary complex circuit. Why do you use a zero cross detector in the MOSFET drive circuit? Also the MOSFET gates are floating when they are not driven around the zero crossing.
Yeah the zero Crossing thing might not work we will see. are floating gate bad. The problem I thought of is if the gates don't fully discharge within one zero Crossing interval.. Couple milliseconds.. The fets could be left partially conductive until the next zero Crossing… which would be bad.
My only suggestion on your mosfet circuit is to have a higher rail than 5V to minimize rds on. I can't make out the part number but for power mosfets typically you want a high vgs drive. Check the data sheet to see what it says, but I would think it would be around 15V to get the rated rds on minimum. You are driving a 20ohm load so rds on is especially critical.
@bennettslab2084 you aren't doing any fast pwm switching so really a gate driver is not all that important. If increasing your rail is a pain, you could slap a charge pump like the TC7660EOA713. Which you can configure to double your rail from 5 to 10(minus some diode drops so schottky diodes are prefered)
@@feloria1862 The isolation transformer i'm using has a few outward voltages. So It wouldn't be a problem. The driver is more just proof of concept... All of these projects are just practiced for myself.. it's the best way to learn what really works
i do not get the point of this exercise. why not using off the shelf heater components, they are dead cheap out of amazon and ebay if you take the crappy ones. all the electronics and calculation stuff you can do on those 15 ohm ones too.
This is a Darwin Award just waiting to happen.
I have similar reservations about it. Typically you don't water cool. Resist your elements until 15kw+ but I'm just messing around here. It's really more of a size trade-off.
Resting the variac on the edge of the bath - what's the worst that could happen? :D (Yes, I know an RCBO should trip first, but... yeah :) )
@@Telukin An RCBO or GFCI wouldn't trip if the fault happens after the automotive transformer. And at least for these types of tests, I doubt much would change if DC was used instead of AC.
The comical enjoyment outweighs the danger.. :]@@Telukin
Isnt that another way of saying water heater element ?
That would be too simple. Haha
With enough amps a copper wire in a 5 gallon bucket can be a water cooled resistor 😂😂
You know, instead of that big complicated driver circuit for over-temperature protection, you could just use a couple of bimetallic temperature switches in line with the resistor instead. (That is how this sort of thing would typically be protected in any real-world product anyway)
Also note that if your water is actually in contact with the leads of the resistors (which it will be unless you've been very careful with sealing them all off), then the total resistance of the apparatus can theoretically change depending on the mineral content (hardness) of the water you are using. You can also potentially get some leakage current between your voltage source and ground (which would, for example, cause problems for GFCI devices, etc).
This is all very true. I did attempt to seal the resistor pack but I would not rely on that for a long operation. My water here is about 1.5M ohm / in. Although I think I'm going to use this heater For a heated patio or driveway when it snows. We will see.
I did ground the chassis. And it does not work with GFI outlets haha.
the continuous flow heater has already been invented.
In Germany three resistors each at 230V AC, three phases 400V. The pipe is grounded and it doesn't matter.
Why not just use one of those electric heater elements? They are about 15 ohm. It's gonna be a lot safer and less janky.
ture, tho, Not as fun
Water cooled resistor.. that's something new😅
How to upset your girlfriend.
Ah, who am I kidding? We both know there's no girlfriend.
Sorry bro. I only lash out to hide my own shame. Cool resistor, man.
hahaha i love itt.
I think that using the voltage and current is probably the most accurate way to measure the power since your resistor changes with temp.
You could also plug a kilowatt power meter (240V version ofc) on the output of your variac and get a power measurement there.
You want to do it on the output of the variac instead of the input because the variac is not 100% efficient. So placing it on the variac output gets rid of that power loss from the measurement.
I could also put a fixed amount of water in it and run it for a fixed amount of time in a thermal Anechoic chamber… If accounting for the change in fixture temperature the change in water temperature could tell us the exact power input.
what fun.
Good grief man, just get a wire wound ceramic resistor.
They're made to go over pipes for cooling.
Come to think of it, power resistors are actually pretty easy to make.
All you need is nichrome wire and ceramic tube, cover the whole thing in glaze once you get the resistance right, fire it and you're done.
Your gap between the resistors and the pipe isn't helping your heat transmission any.
Fill it with sand.
An unnecessary complex circuit. Why do you use a zero cross detector in the MOSFET drive circuit? Also the MOSFET gates are floating when they are not driven around the zero crossing.
Yeah the zero Crossing thing might not work we will see. are floating gate bad. The problem I thought of is if the gates don't fully discharge within one zero Crossing interval.. Couple milliseconds.. The fets could be left partially conductive until the next zero Crossing… which would be bad.
Resistors are lame, what's the use case for something like this? Aside trying for 'death by misadventure' on your death certificate.
Comic relief and possibly heated patio driveway. We will see
My only suggestion on your mosfet circuit is to have a higher rail than 5V to minimize rds on. I can't make out the part number but for power mosfets typically you want a high vgs drive. Check the data sheet to see what it says, but I would think it would be around 15V to get the rated rds on minimum.
You are driving a 20ohm load so rds on is especially critical.
The best mos driver i like is the (fin 32)
It's simple and fast.
And I do need 15 volts not 5. lol
Yeah the Miller plateau…
@bennettslab2084 you aren't doing any fast pwm switching so really a gate driver is not all that important. If increasing your rail is a pain, you could slap a charge pump like the TC7660EOA713. Which you can configure to double your rail from 5 to 10(minus some diode drops so schottky diodes are prefered)
@@feloria1862 The isolation transformer i'm using has a few outward voltages. So It wouldn't be a problem. The driver is more just proof of concept... All of these projects are just practiced for myself.. it's the best way to learn what really works
i do not get the point of this exercise. why not using off the shelf heater components, they are dead cheap out of amazon and ebay if you take the crappy ones. all the electronics and calculation stuff you can do on those 15 ohm ones too.