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PostPosted: Thu Dec 12, 2013 1:22 pm 
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Location: Bournemouth
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Interestingly, the power driver chip I mentioned earlier in the thread - VN5016 that I commented seemed very small to be a 40A device is now listed as discontinued in RSwith the suggested alternative being a near identical device but rated at 18A. Still listed on the manufacturers website as 'current production' though which is puzzling.

The new control board design for our electric vehicles has now gone for manufacture, and the radio board part of the system now has a working prototype.

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This is slightly off topic, but I'm posting as it's actually very relevant. It's a system operating in an automotive style environment (temperature variations, damp, vibration) using canbus to communicate between modules, and is using the same devices that will be final PDU design. A very good test bed.

I will be going ahead with the PDU, at least for my own use, probably around the end of next year. The hardware & software design is pretty straightforward and with both my GT4's starting to suffer from ropey electrics will be less work than rewiring the cars with standard looms.
Whether I then go on to pay for E marking and market it is another matter to consider when it has a year or 2 use under it's belt.

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PostPosted: Wed Dec 18, 2013 7:31 pm 
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PostPosted: Wed Dec 18, 2013 8:31 pm 
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PostPosted: Sat Dec 20, 2014 7:14 pm 
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I thought I'd give this an update as the electric vehicle system is now up & running and ready to go for a first production batch.

The plan is to get at least half a dozen of our electric vehicles equipped with this for the 2015 season to give a good initial test of reliability.

The first prototype above ended up with a few tweaks as shown in the picture below. I had to change the regulator to a switchmode type (hence all the components bodged on) as the linear one was getting hot. I also added a reverse diode on the power relay contact so that if the relay dropped out while the motors were being driven it didn't overvolt & destroy the drivers.

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This worked reasonably well but the motor driver chips were on their limit running our smaller vehicles. These use a cheap direct drive wheelchair motor / wheel combination geared for a top speed of 5 - 6 MPH. Since we run at maximum 3MPH these therefore need more current running at 12V than if geared for the correct speed at 24V. The system worked fine running with a 12V battery, however all our vehicles out there (30+) run on 24V and the chargers are well over £100 each. The cost of changing, plus the operational nightmare of some vehicles running 12V and some running 24 doesn't bear thinking about.

Therefore, on the second iteration I doubled up on the driver chips running 2 in paralell for each motor. This effectively halves the current and therefore quarter the heat for each chip - halving heat generation overall. These are now working well and I'm hopefull may be powerful enough for our 2 tracks with hills.

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The complete system for an electric vehicle is now a control unit plus radio on the chassis with a single loom plugging into the larger socket on the control unit. The body carries a junction box for joystick and fire button, plus the elctronic unit for the anti-collision sensors - a bought-in parking sensor system. This links via a single 12 core cable to the small socket on the control unit. Ultimately, I will probably put a small canbus interface in this junction box then the body can connect via a 4 core curly telephone type cable.

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The radio and control units are communicating via canbus, and the radio has a USB interface so I can plug in a laptop and get full diagnostic information out. Basic 'error codes' are also passed via radio to the control system on the track / arena to provide plain text fault messages to the user, and then also send me a text message alerting me to the problem. (All our coin units / track control units have a GSM modem).

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