Timed relay question

[mr bob]

Hi all

This is my 1st post and 1st project, i feel ive got as far as i can with my (very very little) knowlage of electronics, i feel i need some help getting the finer details sorted out so im here to ask your help please.

The project is really an expantion of an exsisting circut which is an electro/hydraulic roof for a converable car:

**broken link removed**

Currently to lower the roof you have to hold down the switch untill the cycle of the roof has finished, what i would like is to only have to press the switch for a second and for the roof complet its cycle on its own.

What i propose to do is remove the switch (6861 on the diagram above) and replace it with this circut:

**broken link removed**

(apoligies for the poor diagram)

The idea is to use a monostable 556 to hold a NO/NC relay open for 35 seconds (the time it takes for the roof to do it cycle) 1 relay would do up one relay would do down, the standard roof switch ccould be used to control this (its been renamed 6861B on my diagram just to clear that up)

I hope you understand what im trying to do

Where i need help is:

What resistors will i need, what capactors will i need and what diods will i need?

As you can see i havent connected the reset pins on my 556, i would like one direction to cut out the other, eg if the roofs midway though going down, if i press the up button i would like the roof to stop where it is and start going up, however i dont know if reset needs an earth or a V+ to do this.

Most of all, will it work? or will the load be to much and it go on fire?

Thanks for any help you can give me

Bob

 

[Dr_Doggy]

555 timer with relay im sure would work, i didn't really read your schematic

however are you going to override the up cycle with the down cycle too?

the problem is that if you push down for 2sec then override with up, the up cycle is going to keep running pushing the motor for the rest of the 35secs,,

the best options i can think of is to use a micro controller that remembers the position,

OR for a rookie,,, change the 555timer idea with a flip flop, then use 2 push-buttons or sensors to detect when roof is at max points, , and the sensor can RESET the flip flops, and you roof button can SET them

 

[mr bob]

Hi

thanks for the reply, yes i know if its overriden the relay will stay open for the 35 seconds even if the roofs finished ts cycle however the roofs ecu cuts the motor when the roofs finished its cycle even if the button is continued to be pressed so thats not a problem

i have read a bit more about 556's and it seems i had it wrong, ive read the reset and trigger pins need to be grounded in to order to be triggerd so ive redrawin it

**broken link removed**

ive also replaced the standard 2 position switch with a 4 position switch:

**broken link removed**

which looks the very same on the outside as the current switch

**broken link removed**

but the inside has 2 push buttons on each side, one is higher then the other so if you lightly press it one 1 is push if you press it harder both a pressed at the same time, so ive connected the higher one to the opposite sides reset and the lower with the trigger of the direction wanted, im hoping this would mean the roof can be stopped and started by the user?

also im gonna say that R1 and R2 are 10k and R3 is 330K resistors, C1 is a 100µF and C2 is a 0.01µF capacitor which should have a time period of 36 seconds (if i understand it right?)

so anyone think this will work?

 

[3v0]

There may be a reason why the car did not have the ability you want to start with.

Could be the car maker has less liability with the dead man switch approach?

Still you have to think what will happen to the top should something go wrong. For example when closing there is a package in the well were it stores.

At the very least have a cancel switch to stop it.

 

[mr bob]

the roof has its own storage area which is only big enough for the folded roof so there no chance of anything being put in there

**broken link removed**


plus the roof cover is only ever open when the roof is goin up or down so its not like its ever going to be used for anything else

oh and if you switch the ignition off it will stop the roof

 

[Dr_Doggy]

i can't imagine that's too good for your hydraulic to let it run like that....

like i said i'd recommend using 2 flip flops, real easy to wire, just put a trigger to Reset it ,
then hook the SET on to the UP/DOWN of each one, and the Q-pin goes to the H-bridge relay configuration,

Or i would use the Q' Pin and invert it, i find it stableises relays better,

also regulate the dual flipflop since idk if they go up to 12v

 

[mr bob]

once the roof has finished its cycle the hydraulics are shut off, if you hold the button down once its finished nothing happens so if the timer over runs the cycle nothing will happen,

secondly the roof can only be run with the engine off, once the roofs completed its cycle i either switch the ignition off and step out the car or start the engine and drive off so if i had to do either the timer would be shut off anyway so the over run wouldn't be a problem