3Ph BLDC waterpump motor control

[gisqc]

Hey guys,

I have a Stewart EWP and realized that the controller they sell with it lacks any speed adjustment. Turn it on, full speed turn it off nothing, which kind of ruins my plan of not running a thermostat and working with pump speed for warm up and temp control.

I have been looking at bldc motor controllers, sensorless in my case and the all made up solutions gets pricey very quick.

First found a nice chip : Allegro A4915, but that will only work with hall effect sensors. Had a simple analog input for speed control, which could be used with ecu PMW and a smoothing circuit and few I/O's for ON, and direction, integrated gate driver, only needed to be used with 6 mosfets and was ready to go. Well my motor doesn't have sensors.

Found another chip for sensorless motors A4960, similar but with BEMF feature to run sensorless, includes gate drivers to. Speed control is directly from a 5V PMW input which is good. Only "downside" is that the direction, run and brake functions needs to be written in register thru a SPI connection, means I need additionnal hardware just to make it run. Maybe I could leave it on run all the time, it goes to sleep when not used and power it only when the motor is running? Unless an SPI interface isn't to complicated, I'm trying to read on it but it still barely make sense in my head.

Any input, different chips, simple SPI device or anything else?

Thanks

[ol boy]

Check for an RC airplane bldc controller. How many amps does your pump pull? The controllers have came way down in price over the years. In put is a pwm of 900us to 2100us for wot. The refresh pulse happens every 20ms(50hz). A simple picaxe 08m2 could convert a filtered pwm analog input then drive the pwm train to the bldc speed control.

[gisqc]

It says it drains up to about 10amps, circuit is fused at 15 amps. So far anything that came as an off the shelf complete controller wasn't really cheap or wasn't strong enough.

I did find another chip in the same family for sensorless control, A4960. Only requires a FET powerstage and some SPI interface in front of it, not to run it but mostly to configure it (start-up sequence options etc to match motor characteristics), there drives speed directly off a PWM. Found a simple USB - SPI interface board for 15$ that I may be able to program into more eventually. Could read up inputs and act as a standalone programmable pump controller in future (eliminating the need for a t-stat even if not used with a standalone ecu).