Dear Gurus, Below I attach a snippet of a water saving project to see
if there will be any interest. It depends heavily on analog and uC
skills.
Bye
Fred
'It's still cold mum' she cries and the water goes down the drain
We will show a project to save water in many homes.
This project offers unique advantages because:-
*It does not oblige you to have your house rewired to take 50A or more.
*It does not oblige you to get a new contract from the your Electric Utility (12kW+)
*It does address the problem of getting instant hot water using a minimal point of use installation.
And.....
the Project is controlled by cheap 18F uCs
watersaverbasic block2.jpg
How does it work?
Switch on the battery charger to power up the system. .
Charge control can be many things, but we opted for a Lead Acid battery for cheapness.
So basically we monitor the voltage and charge as per one of the standard algorithms and cycles.
e.g. 3 stage charging with electronic sensing that prevents overcharging
The battery. Can be a standard small yacht 24V battery or two 12V car batteries in series. How many ampere hours? We can chose say a 200Ah type. This will give 2A for 100 hours almost certainly. But for our usage it will give 200A for maybe 10 minutes. Later we will see if this is OK.
Resistor Thyristor group. Without entering into the nitty gritty the thyristor is PWM modulated to pass the 200A which are available to a hollow resistor when water is being demanded. As we can see in the math appendix at the end, this is only for about 20 seconds when hot water from the storage tank or main house gas heater eventually arrives. So we need to monitor the temperature of the incoming remote 'hot' water and our heated tap water..
Water Flow hardware.
This can be very simple and cheap or very sophisticated.
Opening the hot water tap starts water flowing.
With a remote main gas heater it will also be started to heat this water flow.
Flow meter. This can be bought for about ( good quality) $350), or we can buy an old domestic water company meter,... or if we feel really inventive we put in the plastic tube a Mississippi steam boat metallic iron paddle wheel that rotates when the water starts moving.
We use a hall sensor and detect when each of the blades changes the magnetic field.
( I would buy the 2nd hand water meter.. maybe €5 )
A typical hot shower using water economiser shower heads is consuming about 12 – 18 litres a minute. The water flow is not conditioned in any way, simply we monitor the temperature of the water having passed through the tubular heating resistor and which is coming out of the shower..
So special hardware previous to the water outlet, tap or shower, or bath is reduced to electrical sensors before and after the tube resistor physically in contact with the water. Ah and a NO WATER sensor for safety.
Water flow monitors.
To elevate the cold water in pipe temperature, maybe only 10ºC we need to heat it instantly, which will require a lot of power. How much power have we got?
We said 200A batteries. 200A x 24V gives about 5kW. As we will see in the calculations appendix this is sort of minimum to go from 10ºC entry water to 35ºC coming out of the shower head.
So following the action, the remote gas heater is sending hot water into the pipe to the bathroom and at a given moment the water appearing in the bathroom is rapidly increases in temperature and is then at the desired 35ºC... in those last two or three seconds of our supposed 20 second wait..
The PWM from the uC rapidly reduces the duty cycle until there is no heating power being drawn from the battery. This reduction in PWM duty cycle is calculated from the water in and water out temperature sensors data.
Installation? A hole in the wall to let those 400A cables get to the heating block of resistor and thyristor. The heating block is physically very small and can be housed immediately below the 400A cable entry. Also the keypad and LCD on the wall to set the temperature desired. Outside some sort of housing for the batteries and charger..
Safety Well by not having 110 or 220V in the bathroom we have a basic electric shock safety. As we will see in the proposed uC routines. What if you deliver full power to the resistor when there is no water? In normal operation the resistor is water cooled by it's usage. , when there is no water, a “NO water'” sensor keeps the thyristor off..
You insist, and if the uC signal to the thyristor is lost.?
Then we use contingency Plan B.. a smoke detector and a sprinkler also call the fire department, police and ambulances.
This brings us to the end of the first part. The next part will cover, the maths involved and ( you will have noticed 400A cables) and the physical parameters we will need..
The third and final part will show the uC program routines required to control the sensors and display the water temperature on an LCD.
Bye
Fred
'It's still cold mum' she cries and the water goes down the drain
We will show a project to save water in many homes.
This project offers unique advantages because:-
*It does not oblige you to have your house rewired to take 50A or more.
*It does not oblige you to get a new contract from the your Electric Utility (12kW+)
*It does address the problem of getting instant hot water using a minimal point of use installation.
And.....
the Project is controlled by cheap 18F uCs
watersaverbasic block2.jpg
How does it work?
Switch on the battery charger to power up the system. .
Charge control can be many things, but we opted for a Lead Acid battery for cheapness.
So basically we monitor the voltage and charge as per one of the standard algorithms and cycles.
e.g. 3 stage charging with electronic sensing that prevents overcharging
The battery. Can be a standard small yacht 24V battery or two 12V car batteries in series. How many ampere hours? We can chose say a 200Ah type. This will give 2A for 100 hours almost certainly. But for our usage it will give 200A for maybe 10 minutes. Later we will see if this is OK.
Resistor Thyristor group. Without entering into the nitty gritty the thyristor is PWM modulated to pass the 200A which are available to a hollow resistor when water is being demanded. As we can see in the math appendix at the end, this is only for about 20 seconds when hot water from the storage tank or main house gas heater eventually arrives. So we need to monitor the temperature of the incoming remote 'hot' water and our heated tap water..
Water Flow hardware.
This can be very simple and cheap or very sophisticated.
Opening the hot water tap starts water flowing.
With a remote main gas heater it will also be started to heat this water flow.
Flow meter. This can be bought for about ( good quality) $350), or we can buy an old domestic water company meter,... or if we feel really inventive we put in the plastic tube a Mississippi steam boat metallic iron paddle wheel that rotates when the water starts moving.
We use a hall sensor and detect when each of the blades changes the magnetic field.
( I would buy the 2nd hand water meter.. maybe €5 )
A typical hot shower using water economiser shower heads is consuming about 12 – 18 litres a minute. The water flow is not conditioned in any way, simply we monitor the temperature of the water having passed through the tubular heating resistor and which is coming out of the shower..
So special hardware previous to the water outlet, tap or shower, or bath is reduced to electrical sensors before and after the tube resistor physically in contact with the water. Ah and a NO WATER sensor for safety.
Water flow monitors.
To elevate the cold water in pipe temperature, maybe only 10ºC we need to heat it instantly, which will require a lot of power. How much power have we got?
We said 200A batteries. 200A x 24V gives about 5kW. As we will see in the calculations appendix this is sort of minimum to go from 10ºC entry water to 35ºC coming out of the shower head.
So following the action, the remote gas heater is sending hot water into the pipe to the bathroom and at a given moment the water appearing in the bathroom is rapidly increases in temperature and is then at the desired 35ºC... in those last two or three seconds of our supposed 20 second wait..
The PWM from the uC rapidly reduces the duty cycle until there is no heating power being drawn from the battery. This reduction in PWM duty cycle is calculated from the water in and water out temperature sensors data.
Installation? A hole in the wall to let those 400A cables get to the heating block of resistor and thyristor. The heating block is physically very small and can be housed immediately below the 400A cable entry. Also the keypad and LCD on the wall to set the temperature desired. Outside some sort of housing for the batteries and charger..
Safety Well by not having 110 or 220V in the bathroom we have a basic electric shock safety. As we will see in the proposed uC routines. What if you deliver full power to the resistor when there is no water? In normal operation the resistor is water cooled by it's usage. , when there is no water, a “NO water'” sensor keeps the thyristor off..
You insist, and if the uC signal to the thyristor is lost.?
Then we use contingency Plan B.. a smoke detector and a sprinkler also call the fire department, police and ambulances.
This brings us to the end of the first part. The next part will cover, the maths involved and ( you will have noticed 400A cables) and the physical parameters we will need..
The third and final part will show the uC program routines required to control the sensors and display the water temperature on an LCD.
