4 out 2 in single step control

[stuartlowery]

I believe this should be so simple I should be slapped but this has stumped me.
Scenario.
2 input buttons 1 step up and 1 step down
4 outputs

Operation

outputs : description

1 On 2 Off 3 Off 4 Off : state at power up
1 Off 2 On 3 Off 4 Off : state after Input 1 is pressed and released
1 Off 2 Off 3 On 4 Off : state after Input 1 is pressed and released again
1 Off 2 On 3 Off 4 Off : state after input 2 is pressed and released

So label Input 1 as up and 2 as down

When pressing up or down it needs to only take one step not step after step until released.
When it reaches 4 it cannot go up any further so it stays in that state.
Same when going down and reaching 1 stop and go no further.

Outputs will be powering relays.

Any ideas?

 

[blueroomelectronics]

Are you using a microcontroller?

 

[stuartlowery]

I have no idea what I want to use you tell me what would be best to use and how to learn what to do and that's the direction I will go. But as of right now I don't know. I have basic analog knowledge but digital I am just a beginner.

 

[stuartlowery]

Anyone? I've been needing this thing for a year now. Trying to control a transmission. Just don't wish to spend $800 for extras I don't need.

 

[adamey]

This is easy to do. A CMOS 40192 counter should work. It has separate UP/DOWN clock inputs which would be the "conditioned" inputs from your switches.

It outputs BCD (binary coded decimal), or 4 bits used to indicate a number from 1-10. To get a single output you can connect these 4 BCD outputs to the BCD inputs of a CMOS 4028 decoder, which is a 1 of 10 decoder and has 10 individual outputs, only one of which would be on at any time.

Normally the 40192 would keep counting up/down when your switches are pressed (when it hits 10 it goes back to 1 and vice/versa). To make sure it stops at 1 or 4 (0 or 3, actually, since the counter goes from 0-9, not 1-10) you need a couple of invertors and AND gates to inhibit the clock inputs from your up/down swiches when you've reached either "end" of your count.


If you pick up a beginners book on CMOS and/or digital electronics you'll find it's pretty simple stuff (when dealing with "hobby" type circuits). What I've typed might not make much sense, but it really is quite simple once you understand logic and gates.

This circuit could be done with only 4 IC's.

 

[stuartlowery]

Also since this will be controlling relays to handle the higher amp loads and to be able to be bypassed in case of failures Heat, cold, moisture etc. since these relays will already be used I can have relay #1 disable the down input. and #4 disable up. unless you wish to continue teaching. I do need to get a book though.

Stu

 

[adamey]

You don't want to use the relays to disable up/down, although I know where you're coming from (using the 87 and 87a relay connections to allow current flow based on whether your relay is on or off).

It's so much easier to use a couple logic gates to do this at the low-level signal side. Besides, relays are like switches - they're "noisy" and require extra circuitry to condition them when using them with digital circuits.

What are you turning on with the relays? Solenoids? Is it important to make sure only one is on at a time? How fast do you need to turn one output off before another one turns on? It might be easier to just simply forget using the relays and use power transistors to operate whatever it is you're controlling.

EDIT: Better yet, there are lots of intelligent power switches (IPS) for automotive use which combine a MOSFET with a logic level input and are ideal for controlling typical loads found in vehicles.

 

[stuartlowery]

It uses two solenoids to change gears.
1On 2Off = First
1Off 2Off = Second
1Off 2 On = Third
Both on = fourth

Something like that.

 

[adamey]

Well, that will require some extra circuitry to "decode" the 1-4 output into what your solenoids require.

When you say "something like that" are you referring to what combinations on on/off select which gears? Cuz it's pretty important to know which outputs select which gears.If it's exactly like the example you gave, then we can figure out what logic we need to "decode" gears 1-4.

 

[stuartlowery]

Ok I looked it up again.
Gear sw1 sw2
1st = On On
2nd= Off On
3rd = Off Off
4th = On Off

Park Rev Neutral = On On