Solid State Motor Drivers (7 replies)
As promised, the attached essay is my account of the developments made at New Forest & District Sailablity for several sailors over the last 10 years after I tired of repairing standard equipment. Prototype was proved by Keith Harris at the HANSA Nationals held at WPSA in 2014 and it continued in use for the following 2 seasons. The current version of this equipment now resides in David Durston's LIBERTY.
Anyone who is a professional Electronics Engineer will undoubtedly have comments and I welcome any observations or inputs for future improvement. I am only an Electronics hobbyist myself who started in the era of valves and magnetic amplifiers where my professional colleagues still chanted "Tune for maximum smoke" (If it works, don't knock it !)
I hope this is of interest to the community.
Very interesting. Tideway is probably in the market for a new end to end system based on something like this. Probably 2 or 3 units.
While we work out what the best solution looks like, we should also be thinking about the possible production process, quantities, indicative costs, including labour, etc. A cheap solution that relies on an unfeasible amount of free labour to produce enough units isn't really a solution. If the market is big enough, then it will be worth spreading production around. But that requires better documentation and testing etc.
A quick update:
As well as a prototype 3-channel driver for Tideway, since the 2018 Sailability Conference I have designed and built several solid-state variants for HANSA 303 (sport), HANSA 303 (2-seat) and Liberty types; each time gaining more useful data on assembling these systems. In the same period, Suresh at Equal Adventure has initiated a more structured Engineering study to determine how this might be carried into the commercial arena. While I cannot speak for EA, it is possible that some conclusion from that study may be reached this Autumn.
Watch this space !
Attached pic is the current 3-channel driver. £2 coin for size comparison.
Size of that unit is 135mm x 80mm x 45mm. Potential for expansion to 4 Ch. within that envelope.
Late update (Dec 2019):
Following some driver problems at Tideway in 2019, I found that the main winch they were using was drawing a current way above the capability of the original driver (15, gusting 25 Amps). The winch concerned looks like a larger HANSA Jib winch on steroids.
On examining the device on the bench, that winch was drawing up to Forty Amps ! -way above the original driver spec and so short battery life, stressed driver and blown fuses start to be explained. It would also promote early failure of a relay-based system. We have not yet established if that was a rogue motor or if it is typical of that particular winch design. As far as the electronics are concerned, the Main winch driver has now been changed to one that is capable of handling current levels up to 45 Amps, further aided by a 'soft-start' driver mode. Overkill perhaps but using a well tried Engineering aphorism: "Don't force it, use a bigger hammer."
Will post any developments on that one when I see another similar winch.
Thanks for your efforts here- much appreciated.
The attempt to get some commercial involvement with this equipment has come to nothing, probably because the sales volume is too small to be viable. Nevertheless, full details of my designs have been freely sent to correspondents in Hong Kong and Australia so there remains a clear need.
Out of interest, I have recently given a routine service to the gear that was originally built for Keith Harris way back in 2012 and which now resides in David Durston's LIBERTY. Although the control circuitry has migrated to printed circuit instead of Keith's 'rat's nest' stripboard prototype, that original motor driver module remains unchanged after 10 years use and still working 100%. What relay systems could match that endurance ?
The only failure of which I am aware was the Tideway unit as described (Dec 2019) above. I have not been made aware of any other winch motor problems.
Thanks Spike. Just to add that the two Tideway sets were left in the boats during lockdown but worked perfectly despite the neglect. Thank you for your efforts
Thanks for the positive feedback Simon, that's reassuring. However, even critical feedback is useful to improving the breed and design maturity.
My advice for routine maintenance is to apply electrical contact grease to the connectors (system connectors outside the electronics box) after immersion/drying, or at least annually. See original description in "Connectors" thread for type and supplier,
RAE Farnborough 'Magic Fix' for experimental equipment = Undo all connectors and lubricate/grease. Reconnect and the problem frequently goes away.
The worst type of fault is "No fault found" at the workbench !