Help adding to a previous P-MOSFET project

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woodworkerjb

Joined Mar 20, 2012
7
A few weeks ago I was lucky enough to have help on a project from DL324. That discussion subject was on how I could get a remote to energize a 12 volt 4 amp automotive solenoid. After all of my failed attempt Dennis came up with a great circuit that worked like a charm. Now I am further into the project and have determined I need to add to this circuit so that I can make it a latching circuit. The 4 channel remote is a momentary switch type and I need to push on push off. I have posted DL324's circuit for completeness. Any suggestions would be appreciated.


 

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Papabravo

Joined Feb 24, 2006
12,894
Without understanding the nature of the pushbutton remote and the decoder for the pushbutton remote it is hard to visualize the best way to go. Many remote control devices repeat the command associated with a particular button as long as it is held down. Some devices send a unique code for the button, and then send a REPEAT code as long as the button is held down. Debouncing a button is another issue that is hard to imagine from just the data provided. Also are you thinking of using an IC for the latch or do you want something in a discrete transistor design?

Real Estate is LOCATION, LOCATION, LOCATION
Electronic Design is REQUIREMENTS, REQUIREMENTS, REQUIREMENTS

Are you familiar with the operation of a JK Flip-flop?
 

Papabravo

Joined Feb 24, 2006
12,894
IMHO, a CD4027 Dual JK Flip-Flop should be considered. You'll need to figure out some logic with respect to the available signals and you'll need some way to synthesize a clock.

I'm not sure what reliability refers to. Can you elaborate on what factors you think the reliability of a circuit might be compromised?
 

dl324

Joined Mar 30, 2015
9,993
You could wire a JK or D flip flop as a toggle flip flop. Both would require you to reset them at power on if you want them to initialize in a known state. Your switch would provide the clock signal. Can you take it from there?
 

dannyf

Joined Sep 13, 2015
2,197
Any suggestions would be appreciated.
1. Unless for some reason the relay has to be grounded, using a high-side switch is unnecessary here. A low-side switch is sufficient.

2. There are a lot of one-on / one-off circuitry. Yours can be easily modified to do that. If you can find it via google, let me know.
 

dannyf

Joined Sep 13, 2015
2,197
The general thought process is to use the output of your device to latch the input -> positive feedback.

Typically it can be done via a flip-flop (a 555 timer can be configured as a flip-flop for example), some inverters (both logic gates or transistors / mosfets), or a mcu (either custom programmed or via PLC).

Fairly straight forward.
 

dl324

Joined Mar 30, 2015
9,993
Here's something for you to think about:
upload_2016-1-3_21-2-40.png

Your control is 5V, but the rest of the circuit is operating at 12V.
 

crutschow

Joined Mar 14, 2008
24,324
I was going to suggest a circuit similar to that of dl324 but he beat me to it
But note that if the 5V signal if from a relay on the receiver then the circuit may need an added debounce circuit in front of the 4013 CLK input.
Do you know if the receiver does have a relay output or is it just a 5V pulse?
 

dl324

Joined Mar 30, 2015
9,993
I didn't complete my thought regarding the 5V control signal.

The rising edge of the clock to the flip flop needs to be within a few volts of it's supply voltage. That's what Q1 and Q2 do.

C1 is to initialize the flip flop in the set condition. The time constant is around 10,000 times the minimum set pulse width required.

As crutschow mentioned, if the control switch has any bounce, the flip flop clock will require debouncing.
 
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