BMW K bikes (Bricks)

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Akira-80

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Hello everyone. I have installed new cluster Acewell 2853 in my Bmw k100 of 1984. It seems that everything works with the exception of:
- fuel sensor (always is with the indicator of few fuel).
- neutral position of rear box.
Somebody have installed this cluster and can help me? I have read that magic box Beep 3.0 could be a good solution.
Many thanks in advance.

    

robmack

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Fuel sender: The BMW fuel level sender is opposite to Japanese fuel level senders, which is what the Acewell is expecting. You have to modify the fuel level sender to be compatible. Read my page on Messing with the In-tank Fuel Sender.

Neutral: What are you using to decode neutral coming from the TGPI switch? From the sounds of it, you aren't using anything. If not, then you'll have to get a device to decode the switch. This can be the MaruLab's BEP 3.0, my TGPI v5.2 board or the 4-relay circuit (I also manufacture and sell such a board).


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1987 K75 @k75retro.blogspot.ca
2011 Moto Guzzi V7 Racer
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Akira-80

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@robmack wrote:Fuel sender:  The BMW fuel level sender is opposite to Japanese fuel level senders, which is what the Acewell is expecting.  You have to modify the fuel level sender to be compatible.  Read my page on Messing with the In-tank Fuel Sender.

Neutral:  What are you using to decode neutral coming from the TGPI switch?  From the sounds of it, you aren't using anything.  If not, then you'll have to get a device to decode the switch.  This can be the MaruLab's BEP 3.0, my TGPI v5.2 board or the 4-relay circuit (I also manufacture and sell such a board).
Hello Robmack. First of all for your fast reply.
- regarding fuel sensor: this is my fuel sensor. It is the oldest model:




It is not the same sensor that you have in your brilliant explanatory file. My sensor is oldest and has not float (swimmer). So i suppose i have to do different actions. I think my sensor has 2 thermistors (each one for 2 low level message warning). I think the lowest resistor in my sensor is more that 500 Oh and this is the main problem.
IN that event, what do you think would be the best solution? would it works if i change the original thermistor for other with lower resistor? for example 100 Oh at 20ºC?
For the other hand, Acewell Ace-2853 cluster can set up the value of the resistor: you can choose between "of", 100 Oh, 250 Oh, 510 Oh, -100Oh, -250 Ohn and finally -510 Oh. I f i select 510 Oh my cluster in always with the fuel low message warning. If i select -510 Oh the cluster always is full of fuel so i suppose it is neccessary something more.
Best regards

    

robmack

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What you want to do can't be done.  That sender is not directly compatible with the Acewell.  You would need repurpose the sender circuit from the OEM gauge cluster or install a MaruLab's BEP 3.0 to generate a usable signal from that sender.  Even so, the only signal you would get would be a 7L or 4L activation signal.  This is enough to turn on/off an indicator; it is not possible to drive an analog scale inside the Acewell.


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Robert
1987 K75 @k75retro.blogspot.ca
2011 Moto Guzzi V7 Racer
http://k75retro.blogspot.ca/
    

Akira-80

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I take for granted that i am only going to have the 4l signal but it is more than nothing. This signal could be showed changing the thermistor as i explained in my precious email? If not, Beepp 3.0 would be enough to get this signal ?(4l or 7l).
Other option could be change the tank with the fuel sensor for the next model? (The same as your tank and sensor?)
Thanks again

    

robmack

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No, unfortunately you won't get any fuel level indication with just the plain thermistor; you need a constant current driver and a comparator.  The thermistor needs to be heated up to work and this is done with a 95mA constant current sent through the device. When immersed in fuel, the thermistor has one resistance, when in free air it has a different resistance. The resulting change in resistance is sensed by a comparator and the output of the comparator drives a darlington transistor which switches the indicator on or off.  Without a BEP 3.0 or a way of adapting the OEM fuel sender driver, you're out of luck.

Changing the tank for a later tank is not possible either.  The 83-85 model tank is fastened to the frame using a bolt through a central bridge across the frame.  The post-85 tank fastens to the frame using locator pins on either frame member.  You'd have to modify the frame you have plus get the tank.  Not an economical option.


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Robert
1987 K75 @k75retro.blogspot.ca
2011 Moto Guzzi V7 Racer
http://k75retro.blogspot.ca/
    

Akira-80

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Thanks again for your complete explanation. So i have few options. Just use beep 3.0. Have you got some instructions of how beep must be connected? It is necessary the genuine connector (similar shape of euroconnector for tv) of the motorbike electrical plant?? Would beep solve the issue of the neutral position of the gear?

    

robmack

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Instructions for the BEP 3.0 are here:  https://cafe4racer.eu/en/others/296-marulabs-bep-3.html

I'm not sure I understand your question about the shape of the connector.

Yes, BEP 3.0 will solve the issue of decoding neutral.

As an alternative, you might consider stealing the fuel sender driver board from the OEM gauge and adapting it to your bike.  Then build the 4-relay neutral detect circuit for a few Euro.    You could save big.


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Robert
1987 K75 @k75retro.blogspot.ca
2011 Moto Guzzi V7 Racer
http://k75retro.blogspot.ca/
    

Akira-80

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Thanks again. With this circuit (3relays and 1 diode) i solve the issue of the fuel sensor? It is not necessary change the thermistor? For the other hand i have more questions. Excuse me, i make a lot of questions but i want to be sure.
- what are the parameters of the relays? Diode 12v but i need the parameters of the relays
-where is placed this circuit? In your diagram, which is gear position switch and switchedn12v+?
- do you have the electrical diagram of this circuit? (Standard symbols not block diagram).
Many thanks

    

robmack

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@Akira-80 wrote:Thanks again. With this circuit (3relays and 1 diode) i solve the issue of the fuel sensor?
No, it does not solve the problem with the fuel sender. It solves the problem with the neutral light.  The two systems are totally independent from each other.

@Akira-80 wrote:It is not necessary change the thermistor?
You don't have a choice.  You can't change the thermistor; that won't solve anything.  The only solution is to equip your motorcycle with a circuit that works with the sender you have.

@Akira-80 wrote:For the other hand i have more questions. Excuse me, i make a lot of questions but i want to be sure.
- what are the parameters of the relays? Diode 12v but i need the parameters of the relays
Any relay that is Single Pole Single Throw, 12 VDC coil, and contacts rated at 1A @ 125 VAC will work.

@Akira-80 wrote:-where is placed this circuit? In your diagram, which is gear position switch and switchedn12v+?
You can place the circuit inside the relay box.  There you will find the required switched 12V on the Connector for Accessories.  The Gear position switch wires will be found on the OEM cluster connector, and they will need to be brought back to the relay box for connecting to the circuit.


@Akira-80 wrote:- do you have the electrical diagram of this circuit? (Standard symbols not block diagram).
The circuit diagram is below:



Don't worry that the schematic shows two diodes in parallel; only one of them is required.


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Robert
1987 K75 @k75retro.blogspot.ca
2011 Moto Guzzi V7 Racer
http://k75retro.blogspot.ca/
    

D'Ecosse

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@robmack wrote:



Don't worry that the schematic shows two diodes in parallel; only one of them is required.

Since that is the starter enable, two diodes (1n4004 - these are 1A rated) used to meet the current load from the Starter Relay (solenoid) 
Or just use a bigger diode
I know it's a 15 ohm coil on the starter solenoid, but think level of margin might be good safe bet. Say 1N5404 - 3A

    

robmack

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A 1N4007 diode or similar is just fine. The current draw from the starter relay is 560mA. A 1A diode will have sufficient headroom.


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Robert
1987 K75 @k75retro.blogspot.ca
2011 Moto Guzzi V7 Racer
http://k75retro.blogspot.ca/
    

Akira-80

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Thanks everyone for your help.
The most important function that i have recover in the acewell cluster is the fuel sensor warning message.
For this function if i am not wrong  i have 2 options:
-buy a expensive Beep 3.0
-steal the fuel sender driver board from the oem gauge and adapting to my bike. Is this part where i have some questions. do you mean that i need the electronics board of the genuine k100 speedometer? if it is of this way, what is the part number of this board? currently i have not the genuine speedometer. And how must it be adapted to my bike?please inform me with more details i would be very grateful.

Regards

    

D'Ecosse

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@Akira-80 wrote:The most important function that i have recover in the acewell cluster is the fuel sensor warning message.
The simplest solution is to connect a 3W incandescent bulb in series with the thermistor (choose whichever of the two you want for your preferred warning level) 
Switched 12V - lamp - thermistor - ground. 
That of course requires mounting a lamp or an LED on a panel 

You can use an LED (including one of those in the Acewell) in place of the bulb but you will need a 50 ohm resistor (minimum 3W) resistor to supply the Thermistor with sufficient current. Effectively the resistor will be in parallel with the LED but it can come from a separate switched supply with the other end of resistor connected to junction of the thermistor to LED Cathode. 
Same process whether one of Acewell indicator LEDs or an external LED.

    

Akira-80

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Many thanks D'ecosse.
Would you have a electrical diagram of the circuit that you mention in your post?

    

D'Ecosse

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Bulb option shown at top 

If you want to use one of the Acewell indicator lamps connect as the lower half - need to add that resistor. 

There is also potential to use the bar gauge - you would use a relay and have 100 ohms on the normally closed and 10 ohms on the normally open - then common of these to the fuel level input - that would have your bar gauge show 'full' for anything other than low and switch to low level when the thermistor switches 


    

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