Assistance with Switchbox Design

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Thread Starter


Joined Mar 5, 2011
I am still in the planning stages of this switchbox design but I am designing a fully programmable (and reprogrammable at the vehicle :D) switchbox with 4 switches, Mode Switch for changing modes b/c it has 3 Modes at least for now (shown by a 7 segment), and an emergency all off switch. Note: if it leaves the switchbox, it needs to leave as 12 volts not 5.

--Primary Use Externally--
To control mainly lighting systems.
One use is to control a strobe light motor in existance. Load measured on switched wire to the strobe motor: 80 mA
Controlling reverse lights manually
Powering LED strobes (These will be among the heaviest if not heaviest load I will put ever on there due that the main hot is what is switched) Probably 1-3 Amps per Strobe and usually turned on in pairs so 2-6 Amps per circuit
Controlling Siren Cutout: Unknown Load-Most likely no more than 100 mA
Controlling Siren Air Horn: Unknown Load-Most likely no more than 100 mA

--Primary Use Internally--
Controlling 4 Momentary Switches, Mode Switch, and Emergency Off Switch
Controlling LEDs Above each Switch
Controlling LEDs for Siren Cutout and Strobe Motor Activation (These two LEDs are the only components needing to strobe)

Built in a 6.25" D x 4" W x 2" H
Primary Microcontroller: Picaxe 40X2
12V-14V unregulated to 5V Regulated: 7805 (Open to suggestions on this)
Note: Current to the module is not an issue and can be extreme if needed (I can run 30 Amp Supply Wire)
This covers the "Front End"

--Questions-- (Mainly dealing with the backend and taking the outputs of the microcontroller and getting 12 volts and significant and ultra high currents)
I don't know whether to run the Logic Out of the 40X2 to an Analog IC to switch on 12 volts to the Base of a Transistor to allow the current to flow from collector to emitter and the emitter out to switched object or use a relay. Relays scare me due to slow switching, needs a good bit of current to switch, and bulkiness (look at space limits above). Which should I choose or is there any other suggestions?

--Special Note--
I am an authorized emergency vehicle in the State of Georgia and have a permit to use emergency lights per GA Code 40-8-92


Joined Apr 20, 2004
Our policy about automotive lighting mods does not allow such discussion. Even though you may be permitted, these forums are public. What one sees, all see.
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