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For some time I having been looking for a way to interface 3rd party systems into Idratek to allow me to monitor the operation of the heating, cooling and ventilation systems in the house (and ultimately control them better) and I came across a small chip that seemed ideal for the job - the HCPL-3700, which is described as an AC/DC to Logic Interface Optocoupler.
Karam kindly provided me with the specification for a typical Idratek digital input and earlier this week I finally found time to make up my first prototype - see photo below. My initial requirement is to monitor AC mains feeds, but as you will see very few components are required (just 2 resistors and a capacitor) as the IC takes care of most things. For a DC version just 2 resistors are needed (no filter capacitor required) - in both versions the resistors determine the voltage trigger level, which in the prototype I set to approximately 160V RMS.
Yesterday afternoon I hooked it up to a spare input on an Idratek module for the first time and am pleased to say that it works perfectly. I powered it from the nominal 12V Idranet supply, so it actually only needs 3 connectons on the low voltage side - Gnd, +12V, Output->Digital input.
I now plan to build a set of these; at the moment I have 3 circuits to monitor, all AC mains (solar pump, brine pump, boiler enable). Each will be mounted in a small plastic box close to my main Idratek panels, with 2-core mains cable running back to the circuits to be monitored. For anyone that is interested the component cost of a single unit is around £6.50; the chip, capacitor and high-spec resistors make up £3.95 of this and the connectors, board and box account for the rest - I obtained everything from RS.
I hope that this is of interest to others - if it is I can recommend the application notes for the device.
Martin
Karam kindly provided me with the specification for a typical Idratek digital input and earlier this week I finally found time to make up my first prototype - see photo below. My initial requirement is to monitor AC mains feeds, but as you will see very few components are required (just 2 resistors and a capacitor) as the IC takes care of most things. For a DC version just 2 resistors are needed (no filter capacitor required) - in both versions the resistors determine the voltage trigger level, which in the prototype I set to approximately 160V RMS.
Yesterday afternoon I hooked it up to a spare input on an Idratek module for the first time and am pleased to say that it works perfectly. I powered it from the nominal 12V Idranet supply, so it actually only needs 3 connectons on the low voltage side - Gnd, +12V, Output->Digital input.
I now plan to build a set of these; at the moment I have 3 circuits to monitor, all AC mains (solar pump, brine pump, boiler enable). Each will be mounted in a small plastic box close to my main Idratek panels, with 2-core mains cable running back to the circuits to be monitored. For anyone that is interested the component cost of a single unit is around £6.50; the chip, capacitor and high-spec resistors make up £3.95 of this and the connectors, board and box account for the rest - I obtained everything from RS.
I hope that this is of interest to others - if it is I can recommend the application notes for the device.
Martin
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