Will a 555 timer accomplish this?

[stuhagen]

Need a circuit that would switch to ground, then un-ground, then ground. This is for a automotive use to "fake" the DVD receiver to allow me to use the screen for engine management gauge displays.

So, turn car to "on"....the circuit would delay 5 seconds, then ground, then un-ground, then ground again until car's ignition is cycled off.

What I cannot figure is the delay issue on start up. The 5 second delay is important because it is a built in timing sequence used to assume the time it takes to reach to pull the E brake up and down. I can manually do this with a simple on-off switch to ground and flip it up and down whenever I drive. But that is a bit hokie.

Stu

 

[Sceadwian]

Two timers. The first one for the 5 second delay which would trigger the second one for the ground/unground/ground

 

[stuhagen]

Two timers. The first one for the 5 second delay which would trigger the second one for the ground/unground/ground

Reading other forums, they claim this TR7 module for around $20 does the trick and needs no building. It is also programmable to suit various needs. It was designed for a specific Brand, but it can be fitted for all by changing the paremeters.

Stu

 

[cabelyn]

What about use a pic? The cheaper I know is pic10f200. It cost some cents and have 4 I/O pins.

 

[cabelyn]

Actuly, PIC10f200 have one timer and internal clock, so you should have just a few external components.
the datasheet is: https://www.electro-tech-online.com/custompdfs/2011/07/41239a.pdf

 

[cabelyn]

there are some time calculators in assembly. If you google it you should find one.
this is a simple routine for 5 seconds delay.

; Delay = 5 seconds
; Clock frequency = 4 MHz

; Actual delay = 5 seconds = 5000000 cycles
; Error = 0 %

	cblock
	d1
	d2
	d3
	endc

Delay_5s
			;4999993 cycles
	movlw	0x2C
	movwf	d1
	movlw	0xE7
	movwf	d2
	movlw	0x0B
	movwf	d3
Delay_5s_0
	decfsz	d1, f
	goto	$+2
	decfsz	d2, f
	goto	$+2
	decfsz	d3, f
	goto	Delay_5s_0

			;3 cycles
	goto	$+1
	nop

			;4 cycles (including call)
	return