Motorcycle Stereo

[Menticol]

Hello guys! Long time no see

Don't be disgusted by the title, I'm not trying to attach a sub woofer to my motorcycle . Recently I had acquired a little helmet-to-helmet intercom (wired, powered by two 1.5v batteries) and it works great. Next natural step was integrating the intercom to the motorcycle frame, including some nice jacks for the pilot and the copilot, and of course feeding it from the motorcycle electrical system.



Having a chat with the copilot was done, now I needed some music. The intercom already has a 3.5mm AUX-IN connection so it looked trivial.

For the "head unit" I got t got one of these "chinese a mp3/fm radio/bluetooth modules. I replaced the existing surface-mount push-buttons with big external push-buttons mounted on the motorcycle dashboard. I also extended the 7 segment display connections to mount the display on the dash.



It worked nicely for a couple of weeks, but weather and electrical interference took a heavy toll on the poor module. It had the bad habit of changing tunes or volume by itself, creating a driving hazard. I didn't mourn it too much when I removed it: FM radio sensitivity was null, settings where not saved when powered off, and the user interface was very messy to use. The module ended straight into the junk parts bin.

Resisting to give up, I got a new "head unit" . I was scared by my experience with the previous module, but I was very pleased after looking the internals of this new player. "Night vs. day", much better construction quality, and different "firmware" or code inside it. I prefer not to reveal the brand, to avoid problems with ETO.

Learning from the mistakes I placed all the system on the motorcycle back trunk, not behind the dash.



The player had no line out other than its 8 ohm speaker. Connecting the speaker output to the intercom immediately hard-rebooted the player. A small isolation transformer cannibalized from an old radio fixed this.



To control the player I did the same modification. The buttons work by shorting the IC inputs to ground, so, four buttons and one common ground.



But... oh hell, I have a problem! the radio on the trunk is 2 meters away from the existing dashboard push-buttons. Naturally sending the cables all the way is no sense, given the heavy interference. I thought about sending a much higher voltage (5V) to drive 4 relays next to the player, but that would take too much space, and let's be honest, the blue case is not exactly eyecandy on a motorcycle. With 4 relays and cables, it would look like a bomb.

Tried using an ULN2803APG to short the buttons to ground at my command, but the player doesn't respond. It does, however, when I connect the cables directly to ground, bypassing the ULN IC.



So, this is it guys, I'm stuck on this part. Any input from you would be extremely valuable, since I don't wanna take the relay route.

Regards

Felipe

PS: I'm not sure if this should be on the blogs section, but the moderators can make a better decision.

 

[KeepItSimpleStupid]

OPTOFETS. They work wonders.

or for better selection, OPTOMOS relays: https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=6&ved=0CD8QFjAF&url=https://www.ixysic.com/Index/graphics/ProductCatalog.pdf&ei=YvNjVcbQHomTsAW81oKYCA&usg=AFQjCNFkkjMLcZ2bldyuC6JIApBb5l7HPg&bvm=bv.93990622,d.b2w&cad=rja

 

[Les Jones]

Felipe,
It would be interesting to know if the inputs are positive or negative with respect to ground. I wondered about suggesting opto isolators but rejected the idea as they would just have an NPN transistor (The same as the ULN2803) so they would probably not work I then thought about a CMOS quad bilateral switch (CD4066) bit after seeing "KeepItSimpleStupid's" suggestion I think that is better. I have not seen opto isolators with FET outputs before.

Les.

 

[Pommie]

Assuming the chip inputs have week pullups built in then you could reduce (hopefully eliminate) any noise by tying them high with a low value resistor and use a capacitor from pin to ground. Something like a 1k resistor from pin to v+ and 0.1uF from pin to GND. Might work, might not but worth a try.

Mike.

 

[Menticol]

Thank you very much KISS, Les and Mike.

These parts look great KISS, however I think importing them would take too much time. The local market is somewhat basic

Answering to Les question, the inputs are positive respect to ground, around 3 v. I wonder why the ULN2803 is not working. It's not a faked or a damaged unit. Or maybe?

Pommie, I wish I tried your method when I installed the first player on the dashboard. However the player inside the trunk is very stable. I'll keep note if the phantom behaviour reappears.

I was thinking another question for you: My first attempt included running two audio cables from the dash to the trunk. They are decent quality stereo cables (ie. two conductors wrapped with a shield that also serves as ground). Running these wires required some effort, even going as far as removing the fuel tank to ensure getting them properly fastened, far from the ignition system and hot parts. Naturally the tank was re-attached afterwards, or the motorcycle wasn't going very far!

One of this cables is busy transmitting the microphone and speaker signal from the pilot's helmet. But the other have no use, since there's no headunit at the dash anymore. What do you think about using that unused stereo cable to transmit the dashboard button orders?

- Maybe using DTMF (I guess some of you will laugh about using that old standard)
- Using a 3-to-8 Line Decoder (not sure if I need three cables plus the shield, making the existing cable insufficient)
- Or maybe sending different voltages according to each pressed button, and somehow interpreting them at the trunk...

Meh, I'm afraid I'm overcomplicating this too much, instead of using the good old relays and a truckload of automotive wire.

 

[KeepItSimpleStupid]

Answering to Les question, the inputs are positive respect to ground, around 3 v. I wonder why the ULN2803 is not working. It's not a faked or a damaged unit. Or maybe?

Many of the buttons are multiplexed. Low power means CMOS logic levels. Not much more than 0.3 V from ground or Vcc, Even though an opto FET goes down to 200 ohms, it doesn't t have a diode drop, So, while I suspect a wide range of resisor values will work, I suspect I diode wont. If a diode won;t work, then...

The 2803 is a Darlington, so your dealing with 2 Vbe drops or two diodes in series.

I've used the Optos. They work wonders

 

[Les Jones]

Looking at the number of buttons I would have expected them to be multiplexed. (As a 3 x5 or 4 x 4 matrix) As shorting the buttons to ground works they cannot be multiplexed. If it was multiplexed then neither side of the buttons would be connected to ground. Also it looks like one side of the buttons is soldered to thick sections of track which is probable ground. I found out yesterday by Googling "opto fet" that there are other manufacturers of opto isolators with fet outputs. If you look at Farnell's website searching for optical fet does not give any matches but optical mosfet does.

Les.

 

[Pommie]

To use the spare wire, you could use diodes at the button end. Using a diode from switch 1 to 2 and 2 to 3 etc will result in 0V if switch 1 pressed, 0.7V if switch 2 pressed then 1.4 and 2.1 for 3 & 4. However, you would need something like a pic chip to turn the voltage into 4 outputs. An 8 pin 16F683 would suffice but it depend on whether you have any programming experience.

Mike.

 

[Les Jones]

Hi Mike,
If Felipe does not have pic programming facilities then al LM3914 LED bar display driver (Set to the dot display mode.) with resistors in place of the LEDs and followed by a CD4051 hex cmos buffer might work at the receiving end.

 

[Menticol]

Hello again guys! I'm very happy to tell you that the project is going great, thanks to your advice.

First step was finding the photo-couplers. Since I go out of work too late and all electronics shops are closed, I ended up cannibalizing a couple of burned power supplies at home.

A very old computer PSU had three Photocouplers inside it (A beautiful, heavy unit, probably hand made, with enormous heat sinks, every component wrapped on heat shrink, not like the crappy cheap PSUs you see today). I googled the label of the three PCs but could't find any datasheet.

The fourth and last PC came from another PSU, and is labelled as Sharp PC817.



Following the Sharp PC817 datasheet:

Pin 2 and 3 went to GND
Player input went to pin 4.
+12V control signal (from the switch on the dash) go to pin 1 via a 1K resistor.

I followed the same arrangement for the obscure-brand PCs.


And it worked!!! Like a charm!!


It was time to add a big and ugly hot glue blob to avoid short circuits


And to keep the new components stationary inside the case


The remaining part is connecting the player to the pushbuttons on the dash. Part of me is tempted to just simple run 4 new cables across the bike, but the other yells at me to stop being a pussy and try the LM3914. Tough decision! Battle of pride and Glory over laziness.

I have some experence with Arduino, unfortunately not with PIC.

 

[Les Jones]

Hi Filipe,
Do not use the CD4051 between the LM3914 and the radio. When I suggested I was thinking it had open drain outputs but it just has normal cmos outputs. You could just drive the opto couplers from the LM3914. You will probably need to do something to adjust the reference voltage on the LM3914 or use a chain of resistors instead of diodes on the push buttons to get the correct voltage steps.
Les.

 

[KeepItSimpleStupid]

For those sharp Optocouplers, Vce(SAT) is really low.

 

[Dick Cappels]

Sorry -not a helpful post.

 

[KeepItSimpleStupid]

Dick:
You made it feel like my post is not helpful which is not helpful. I got the original post.

You should have said:

Deleted. Sorry -not a helpful post.

Dick's post referenced the failed to connect the violation of the terms of source of another website, apologized and encouraged you to come to ETO, not that "Vce(Sat) was really low."

 

[Menticol]

Hahaha if I had not seen Dick's original post copy on my e-mail, I would have thought the same thing as KISS!

Going a little off-topic for a moment, I understand Dick's worries and the fact that in some countries vehicle modification is strictly prohibited. Many enthusiasts from Youtube channels complain about being unable to install turbo, intercoolers, nitrous oxide, non OEM lightning, or various performance accessories, but hey, laws (and their enforcement) is what make first world countries.

As far I have read Colombia's motor vehicle laws, the only forbidden modifications here are these related with generating excessive noise (either from the engine or audio systems), non certified fuel systems, installing stolen or not properly traceable parts, tampering the license plate, and installing lighting that mimics emergency or special purpose vehicles. So, except by voiding my manufacturer's (laughable) warranty, this motorcycle modification is legal.

In my opinion, it's a shame that certain forums ban talking about vehicle modifications. If some irresponsible guy or girl is asking how to make a dangerous / risky modification, let's face it, if not stopped they will do it anyway. A good Samaritan thing is having an expert (or if not available, a John Doe like some of us) to explain them the consequences and why it should not be attempted. That would prevent an accident.

Just my opinion, end of the off-topic!

 

[Dick Cappels]

If I can speak (write) for myself, my original post was not helpful. Sorry to let it appear that I was referring to yours, which was helpful.

 

[KeepItSimpleStupid]

We realized that, but only because we had both posts. I was worried about others reading this thread. thanks.