Is this possible? a circuit that will turn on four 12 volt bulbs

Thread Starter

Rex Houston

Joined Jan 31, 2021
1
Noob here.

I want to design a control circuit that will turn on four 12 volt bulbs lets say. The circuit is controlled by a single momentary switch (On-OFF-ON). One press of the switch up, turns on bulb 1. Press it up again, now bulbs 1 and 2 are on. Press up again, bulbs 1,2 & 3 are on. You get the idea. Once all 4 are on, pressing up does nothing.

Pressing down on the switch will turn off bulbs one at a time. Once all are off, pressing down does nothing.

Can this be done with 12 volt automotive style relays, or latching relays, diodes, etc ? What would the schematic look like? Is this even possible?

I know this would be easy for an arduino or such design but I would like to keep it old school if possible.
 

dl324

Joined Mar 30, 2015
12,871
Welcome to AAC!

You could use a 4 bit shift register (e.g. CD4015) and use the momentary switch to clock 1's into the register. You need to debounce the switch and use BJTs or MOSFETs to switch the bulbs low side.

EDIT: missed the part about shifting the other direction. You need to use a bidirectional shift register for that. Let me look up a part number. MC14194
 

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Marley

Joined Apr 4, 2016
411
Extremely difficult with just relays. Can be done with a shift register as above.
Needs a bit of extra logic to generate the clock and direction signals and de-bounce the switch.
Rough circuit attached.
ShiftRegister.png
 

ElectricSpidey

Joined Dec 2, 2017
1,654
Nice Marley, I was going to post something similar but using a reset set FF and a 555 to delay the register clock...but I like yours better.

(probably needed some inverters as well, but never got that far)
 

dl324

Joined Mar 30, 2015
12,871
Here's an easier to read schematic:
clipimage.jpg
I didn't include caps for debouncing the switch.

The datasheet specifies a minimum setup time on S1/S0 of 75ns before the clock. Without IC1D, there's no delay and the shift direction could be wrong on direction changes.

I didn't know what the lamp current would be, so I used a MOSFET that can be a power type.
 

ElectricSpidey

Joined Dec 2, 2017
1,654
I also like the use of the RC network in Marley's design to provide both the de-bounce and the clock delay.

The 60ns propagation delay on the 4011 might not be long enough for the clock delay.

The RC network can be adjusted.
 

dl324

Joined Mar 30, 2015
12,871
The 60ns propagation delay on the 4011 might not be long enough for the clock delay.
If you think about it, it's not likely to be a problem because the shift register isn't clocked until the switch returns to the off position. That's going to take milliseconds.
 

Alec_t

Joined Sep 17, 2013
12,068
Won't the post #5 circuit just be shifting zeroes?
How will it cope with both the lights on sequence and the lights off sequence as specified by the OP?
 

eetech00

Joined Jun 8, 2013
2,361
Noob here.

I want to design a control circuit that will turn on four 12 volt bulbs lets say. The circuit is controlled by a single momentary switch (On-OFF-ON). One press of the switch up, turns on bulb 1. Press it up again, now bulbs 1 and 2 are on. Press up again, bulbs 1,2 & 3 are on. You get the idea. Once all 4 are on, pressing up does nothing.

Pressing down on the switch will turn off bulbs one at a time. Once all are off, pressing down does nothing.

Can this be done with 12 volt automotive style relays, or latching relays, diodes, etc ? What would the schematic look like? Is this even possible?

I know this would be easy for an arduino or such design but I would like to keep it old school if possible.
Here is a version using standard non-polar 12v relays.

1612215597331.png

1612215631371.png
 
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