Relay switch with MFC-03 help

[Jinya 1]

Hello,

I am fairly new to the electronics and I need help on connecting a light bar to Tamiya MFC-03.

I wish to power up the light bar using a main battery (7.2V, parallel split wiring) as a power source and MFC-03 (J9, J16, J20, J27 LED ports are available and planning to use J20 port) as a trigger.

During my brief research in this forum I found something called "Pico Switch" from Dimensions Engineering. But if I understood it correctly it uses servo port PWM instead of regular LED port (such as J20 port) voltage as a trigger and this was not what I was looking for.

As far as my knowledge goes my only option is to use a relay switch but I don't know which relay is safe to use directly on MFC-03 LED ports.

If possible could someone please pinpoint the suitable relay switch I can safely use  on Ebay or someplace simular? (a seller who ships internationally)

 

Thank you.

 

[Tamiya Fan 1 114]

A "Pico Switch" is the way to go. Unless you don't have an extra channel.  But you want to run it off of J-20. (so your extra lights turn on with truck run lights) 

I get it! That is exactly what I wanted to do In the beginning of my First Knight hauler.  So I experimented for about six months with electronics. (on and off) A lot of failure till I got the circuit right. I am not an electronics guy, just self taught when I was a kid. (Just enough to be dangerous) Any way I came up with a circuit that will do just that. It gets added into all my trucks. When you toggle through the lights, roof lights turn on and so do the extra lights. RE: extra truck lights and added trailer run lights. They are hard wired to trailer along with the Tamiya Trailer light kit.

Unfortunately all forums that talked about this are gone these days. "Mr. Lights" came with a set up that could run as many lights as you wanted. (see if he can still be looked up, but doesn't do them any more). Mine has a current limit, but handles a good amount.

Bottom line is it can be done if you know electronics a little. I don't want to say much more do to liabilities, etc... Not trying to be a D_ _ K. I've thought about this in the past and don't want problems with some one burning up a MFC/Etc...(possibly Tamiya)

You make a "Y" to connect to J-20 on MFC. Roof leds/J-20 connect to one end and circuit to the other. When you turn lights on it's like you pulled the switch in the truck and all running lights turn on. Very realistic, no extra channel. The MFC does it's thing and the circuit does it's thing simultaneously. The circuit runs off the battery but triggered by J-20.

I answered this because that is exactly what I thought way back when. It can be done off of J-20. So you are on the right track. Nothing is available to purchase out there to do this. (I looked/that I know of) A lot of trial and error to figure it out though. I am no electronics wiz, but I came up with it. Is it right?? But does work in about 20 of my trucks. No problems unless I had to many LEDS and it will kick in out, or not light at all.

This got long. Do to Liabilities I don't want to say more?? But your on the right track. An Extra channel will work also. You can figure it out. Your on the right track.

[Tamiya Fan 1 114]

If you run extra leds off of MFC ports, you can only get 1 or 2 extras before the lights won't light because that port will be over current. So you do need something in between Like a relay that powers from battery. But a relay won't drive of of J-20  because there isn't enough power there. Hope that makes sense? I think MFC is some what protected but to much or done wrong could damage MFC $$$$. Be careful !! Also why I don't want to responsible.

[Tamiya Fan 1 114]

I thought about this and remembered I saw something that might work? It is called a "MFC Expander Board". I would put Tamiya in front of that for web search. I have not tried this, I don't see it working with what I know about the MFC. May be it has some circuitry in it to makes it work? It is supposed to plug in to MFC and give you 10 extra plugs to plug in. Not much info on it , does it work?? Note  it is not made by Tamiya as far as I know. This may work for you? About $23, I've seen it on Ebay and a hobby store. 

Let me know if you need help finding it? If it works let us know. Remember MFC's are expensive. Just trying to help.

 

 

 

[Jinya 1]

3 hours ago, Tamiya Fan 1 said:

I thought about this and remembered I saw something that might work? It is called a "MFC Expander Board". I would put Tamiya in front of that for web search. I have not tried this, I don't see it working with what I know about the MFC. May be it has some circuitry in it to makes it work? It is supposed to plug in to MFC and give you 10 extra plugs to plug in. Not much info on it , does it work?? Note  it is not made by Tamiya as far as I know. This may work for you? About $23, I've seen it on Ebay and a hobby store. 

Let me know if you need help finding it? If it works let us know. Remember MFC's are expensive. Just trying to help.

 

 

 

First of all I thank you so much for your long and kindly detailed explanation.

I already looked into "MFC Expander Board" and although I couldn't understand how it works it's main purpose of the usage seems to expand the number of the LEDs connected to the one MFC port. As you already understand I simply need the solution to "How to connect one 6V~7.4V LED to currently empty MFC J20 port" and this board doesn't seem to fit my needs.

I saw some relay module that operates on very low voltage (below V5 maybe?) but I couldn't even figure out the MIN. and MAX. voltage that can be drawn from MFC J20 port safely.

[Tamiya Fan 1 114]

I thought MFC Expander might not be up to par. I THINK you'll get 5volts from J-20. (Haven't looked at my notes) But relay might pull to much current for MFC to sustain it and could do bad things to the MFC. Leds don't draw much current (amps) I would look to something in the transistor switch which will be like a relay but lower current. So look for something like the relay switch but has a transistor instead to turn on/off. Is there something, not sure?? I haven't been up on it lately. The MFC can't handle big loads as I think you know. Transistor is like a electronic version of a relay, low current to operate, trigger it on, where as relay coil will use more current than MFC will provide. I wouldn't feel safe doing it. It's not so much the voltage but the current that the MFC has available. make any sense? 

Hope this helps some what. 

[Jinya 1]

Using relay module as a LED switch might take up too much current for MFC to handle so look for something called transistor instead...right?

Phew voltage, current, this is getting moooore~ complex than I thought.

Anyway thank you for your kind advice again.

[Jinya 1]

Pico Switch from Dimensions Engineering would been perfect only if it used MFC led port instead of servo port as a switch.

[Tamiya Fan 1 114]

You don't have an extra channel on your radio I take it. Pico switch works great for this, if you have radio space. Your on the right track. I wish I could help more, but nothing, I know of is made for this. Maybe an audrino would work, but I don't know much about them.

[M 800STD 527]

Might find something here...

https://www.mr-rcworld.co.uk/shop/category/rc-switches/

[Jinya 1]

3 hours ago, Tamiya Fan 1 said:

You don't have an extra channel on your radio I take it. Pico switch works great for this, if you have radio space. Your on the right track. I wish I could help more, but nothing, I know of is made for this. Maybe an audrino would work, but I don't know much about them.

Your help was more than appreciated and I thank you again.

 

2 hours ago, M 800STD said:

Might find something here...

https://www.mr-rcworld.co.uk/shop/category/rc-switches/

I am afraid that I still don't have enough knowledge on MFC-03 LED port to pick the suitable switch unless the product specification state that the product is specifically designed for MFC-03 LED port.

But thank you for your kindly suggested link page.

 

[Jinya 1]

Someone from the different forum communities suggested me to use the solid state relay(SSR) instead.

Compared to the mechanical relay,  the SSR requires only small amount of current(A) to activate so it will cause much less stress on MFC-03.

I will test out the SSR once I get all the circuit parts I need and let you know if I succeed.

[Tamiya Fan 1 114]

Looks like an optocoupler?  Should have isolation between the two sides. J-20 puts out 4volts with the 2 leds connected. Amps at J-20 not sure?

Let us us know how it all works out.