Old BMS Hardware Thread

[GregsGarage]

How about the Tellymate instead of the SV2000 chip?

If you can get 19200 working with a plain pic that would be great. The data stream from the controller can be set to send at a regular basis so sending the command "rtd-period 1000" would give us a datastream once a second. Problem is that with a software serial port you have no buffer, so if you aren't watching it when it sends the data it is gone forever. One possible solution is to send "rtd-period 10", read the data and then send "rtd-period 0" to get it to stop sending. Or just set it to send a continuous stream and just look at it when you are ready for the data.

I will keep working on the Arduino code, the only hardware required for programming is a usb cable.

[retepsnikrep]

Good ideas Greg.

I'll look again at the tellymate but i do like the tiny chip size of the SV2000. plus i'm familiar with it.

Going back to smoke alarms.

I've been bench testing a bog standard cheapo 9v one and it runs happily at upto 15v supply so can be powered direct from the car 12v battery.

When activated it sounds an alarm and pulses the led. We can piggy back onto the piezo sounder and use the voltage aross it to drive a fet which pulls up/down the interlock input.

The master software can be adjusted to activate the alarms, cut charging etc if any signal if recd from the smoke alarm. This can be a one time trigger so once alarm is activated even if smoke goes away. BMS alarm must be cancelled manually.

I'll post my tiny schematic for the inteface once finished. but it will be similar to the fet layout on the remote rxd board.

The pulses from the smoke alarm piezo via a signal diode charge up a capacitor until fet gate threshold is reached and it turns on.

Peter

[retepsnikrep]

OK Greg we will go with the Tellymate for Master V3 It's a lot cheaper and more flexible. I think I bought one when we discussed it last time must try it. I'm on holiday for 10 days from friday, I will monitor e-mail and have my 2x25cells slave boards to build up when i get back so progress will be slow.

[GregsGarage]

I think we should try and get a pbpro version working with the V2 board first. Then start with the V3 board. The price is right for the Tellymate, you can also download the hex files and program your own.

Another nice feature for V3 would be a serial to ttl converter. I need this for comms with my controller as the serial port voltages on the controller are +/-10v. There seems to be 2 ways of doing this. One is with a chip such as a MAX232 plus some capacitors and resistors. The other option is a simple circuit with 2 transistors, capacitor, diode and some resistors. The second circuit uses fewer parts, but the MAX232 circuit may be more resistant to noise. I have a small board with the second circuit on it, so we can see how that works before deciding which one to use.

Greg

[retepsnikrep]

Simpler is best IMO. Send me a link to the circuit.

Need to decide what we are going to use the master pic hardware usart ports for?

Two way Comms with your controller?
Comms with the slave boards as now and this may enable the data speed to be increased/doubled to 19,200 or higher?
Comms with the tellymate which can receive data at upto 57,600bps?

The tellymate has a lot more screen area so the time to draw it at 9,600 bps may become significant.

We do have the option of using 'debug' as a speedy serout command in pbpro so we may be OK dedicating the serial hardware to your controller. In fact I think that will be easiest.

I agree a test version for Master V2 will have to be developed with the bare bones of the software. Getting the config bits and defines correct at the start of the pbpro program is the most difficult part!!

[GregsGarage]

RS232 to ttl converter. I am using the one mentioned in the article from Sparkfun. Originally tried to build the circuit on a breadboard but couldn't get it to work, but I think that I wasn't connecting it properly. Might give the breadboard one another try now that I know it works.

Do you think the 9600 baud with the tellymate will be a problem? We only need to update changing information after thje initial draw. I can have a play with my Tellymate and the arduino set to 9600 and see if it makes a noticable difference. Will let you know.

Greg

EDIT: Just ran one of the sample tellymate programs, Random Characters, at 9600. Yes it is slower but I think it would still be acceptable.

[retepsnikrep]

That RS 232 converter circuit seems nice and easy, no reason we should not include that on Master V3 ASFAIK. We could perhaps have dip switches/jumpers to switch the Master hardware usart interface to either the video chip or the external rs232 interface as reqd. I would prefer some optical isolation between controller and BMS, wonder if we can include a couple of optos? Do you want to tinker with that?

The current Master software draws the complete screen every second but we don't notice unless the data has changed.

16 x 9 = 144 bytes SV2000 Chip takes about 1/10th second at 9600baud

38 x 25 = 950 bytes Tellymate Chip that could take over half a second at 9600baud which is a good chunk of our one second time slice!

We def need to aim for more serial speed for the video interface. I'll do some testing when I get back from hols in two weeks. We could of course only update the parts of the screen that need it, but that needs cursor control bytes and accurate positioning. Not impossible. Have to see.

[GregsGarage]

I will look at a couple of optos for isolation. The controller logic board is isolated from the traction pack and the instructions also clearly state that the 12v logic supply must be seperate and isolated from the traction pack. Don't know if this extra level of isolation is really necessary but will see what I can find.

Greg

[dillond666]

Hi Guys,
Just ordered one of these to monitor my charging current. Seems cheap so I thought it worth a punt!

http://www.coolcomponents.co.uk/catalog ... cts_id=474

Derek

[GregsGarage]

That should be fine for measuring charging current. That device can only measure current in one direction though. My controller can provide battery current and Ah data for the motor, so I am also looking at using a small current sensor for battery charging, but I also want to measure non-motor loads like heater and DC-DC converter. So I will either use one of the Allegro sensors that Peter got for his or a LEM LAS 50-TP/SP1 that I have lying around.