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<blockquote data-quote="rstrouse" data-source="post: 198" data-attributes="member: 55"><p>I have built 6 diy pool controllers, all using Sequent cards as their backbone. Equipment control for items such as pumps, heaters, chlorinators, and some valves are all done via RS485 (not modbus). These protocols are unique to the manufacturer and often operate at different baud rates. For instance, all Pentair equipment operates at 9600 baud and Hayward operates at 19,200 for pumps and 9600 for AquaRite. There are a number of off-branded pump drives out there that have a modbus interface but if you look you will not see broad support for them. Jandy is another thing altogether and most of the projects out there have been abandoned.</p><p></p><p>Valve actuator control is <strong>24vac (750mA)</strong> and requires a NO-COM-NC relay since one side of the valve must be powered at all times for proper operation. Typically no more that 3 valves are in transit at any given time. This also includes endstop valves actuators supplied by a number of manufacturers. The high power relays typically use <strong>24vdc </strong>coils with flyback isolation. These can be NO-COM relays.</p><p></p><p>Temperature sensors that exist for easy installation in a pool setting (UV and chemical resistance) are 10k thermistors. There are tons of them out that already come with PVC jacketed wire that is potted into the sensor. They are around 20 bucks a pair and will last a lifetime. On the typical pool there are 3 that are used to identify heat demand (water temperature), solar capacity (solar temperature), and air temperature. When the pool is a dual equipment then there is a pair for water temperature of each body and the air and solar temperature are shared.</p><p></p><p>When it comes to chemistry control. You will need at least 2 isolated carriers and 1 non-isolated. The amplifiers in the Atlas pH and ORP circuits are sensitive to all that noise on the equipment pad and must be isolated. The third carrier is for an embedded temperature sensor that is used to calibrate the pH probe as output from that is temperature bound. With many of the probes for use in a non-laboratory environment the temperature sensor is located in the probe itself. In the Pool world dissolved oxygen is not that common. Not sure what that would get you in a wide open body of water anyway. TDS sensors can be useful only to the extent that they reflect the salt levels in the water when the proper factors are applied to fresh water.</p><p></p><p>The most common peristaltic pumps out there are either 120vac or 24vdc. So power considerations on the controller need to be take into account. A single 24vac power supply can be used if there is the ability to power the pi using 24vac like you can do with the BAS. This same power supply can then be used to power valves. If there is a desire to use 3hp relays (kinda required for 2-speed pumps) then a rectifier or a separate 24vdc psu can be used that also powers the peristaltic pumps.</p><p></p><p>While I have seen a number of folks out there switching RS485 pumps and heaters on a relay, that is flat wrong and should not be done. They should be powered at all times. The internal workings of the pump drive and the heater control board understand a call for heat and perform all the appropriate switching. Only single speed pumps should be switched in this manner and most states have outlawed them for pool use. If a heater is tied into a spa/pool scenario this should be switched on the filter relay.</p></blockquote><p></p>
[QUOTE="rstrouse, post: 198, member: 55"] I have built 6 diy pool controllers, all using Sequent cards as their backbone. Equipment control for items such as pumps, heaters, chlorinators, and some valves are all done via RS485 (not modbus). These protocols are unique to the manufacturer and often operate at different baud rates. For instance, all Pentair equipment operates at 9600 baud and Hayward operates at 19,200 for pumps and 9600 for AquaRite. There are a number of off-branded pump drives out there that have a modbus interface but if you look you will not see broad support for them. Jandy is another thing altogether and most of the projects out there have been abandoned. Valve actuator control is [B]24vac (750mA)[/B] and requires a NO-COM-NC relay since one side of the valve must be powered at all times for proper operation. Typically no more that 3 valves are in transit at any given time. This also includes endstop valves actuators supplied by a number of manufacturers. The high power relays typically use [B]24vdc [/B]coils with flyback isolation. These can be NO-COM relays. Temperature sensors that exist for easy installation in a pool setting (UV and chemical resistance) are 10k thermistors. There are tons of them out that already come with PVC jacketed wire that is potted into the sensor. They are around 20 bucks a pair and will last a lifetime. On the typical pool there are 3 that are used to identify heat demand (water temperature), solar capacity (solar temperature), and air temperature. When the pool is a dual equipment then there is a pair for water temperature of each body and the air and solar temperature are shared. When it comes to chemistry control. You will need at least 2 isolated carriers and 1 non-isolated. The amplifiers in the Atlas pH and ORP circuits are sensitive to all that noise on the equipment pad and must be isolated. The third carrier is for an embedded temperature sensor that is used to calibrate the pH probe as output from that is temperature bound. With many of the probes for use in a non-laboratory environment the temperature sensor is located in the probe itself. In the Pool world dissolved oxygen is not that common. Not sure what that would get you in a wide open body of water anyway. TDS sensors can be useful only to the extent that they reflect the salt levels in the water when the proper factors are applied to fresh water. The most common peristaltic pumps out there are either 120vac or 24vdc. So power considerations on the controller need to be take into account. A single 24vac power supply can be used if there is the ability to power the pi using 24vac like you can do with the BAS. This same power supply can then be used to power valves. If there is a desire to use 3hp relays (kinda required for 2-speed pumps) then a rectifier or a separate 24vdc psu can be used that also powers the peristaltic pumps. While I have seen a number of folks out there switching RS485 pumps and heaters on a relay, that is flat wrong and should not be done. They should be powered at all times. The internal workings of the pump drive and the heater control board understand a call for heat and perform all the appropriate switching. Only single speed pumps should be switched in this manner and most states have outlawed them for pool use. If a heater is tied into a spa/pool scenario this should be switched on the filter relay. [/QUOTE]
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