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Wireless Shift Box, Slight Redesign Help Needed.

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Junior Member level 2
Nov 10, 2005
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**broken link removed**

This is a wireless relay circuit, which latches relays as you push buttons. But the problem is, they all stay on. The circuit needs to be changed so they can sequentially latch and shut off by pressing the buttons.

I was looking at the datasheet for the flipflops, and pins 4,10 are for the reset. It seems they have the resets all isolated using that capacitor.

What exactly would it take to make only one relay stay on at any given time? It has to latch when a button is pressed, then unlatch when the next button is pressed.

There are many advantages to this shift box. For one, The transmitter is 12v powered, and wireless (obviously) so the switches could be mounted on the steering wheel allowing your hands to never leave the wheel. The battery I will replace with a 12v lead that will tap into the horn's 12v power source. I will also replace the buttons on the remote with switches and hide the trasmitter underneath the horn cover (haha the modle car this is mad for does not have airbags) This entire circut, actully comes up to be cheaper to build than the wired one, and much cleaner and professional.

I dont really have that option. I need to keep the cost low, and do not want to build any PBC's. I'd like to modify the existing circut to accomidate my needs, which should be possible.

Im looking for a chip that will take ~5v in, constant voltage in, 4 inputs in, 4 inputs out, but only allow one output to be energized at once. My circut does not turn one circut off when the next circut is energized, and I need a way to change that so that only one circut is engergized at a time. When circut one is on, and circut 2 is energized, circut 1 needs to be shut off, etc etc. It currently uses dual flip flops to energize relay circuts, there are two flipflops. Im hopeing to find one additional IC I can use, or maybe a different form of flipflops. These boards are pre-made, so rebuilding/adding tons of stuff isnt an option. I do not want to add additional relays, unless it is one. I need to keep the cost of these down, and keep the entire unit in a small box. Currently, the board allows me the choice of momentary and latcing relay behavior. If it's possible, I could use the momentary pulse from the flipflops that would normally go to the flipflops, to trigger a different form of chip/mechanism. My goal is to get this done without adding more than 3 componets, and hopefully without the need of making/buying more PCB's.

Reciever:: **broken link removed**

dunno if this will help, but.....


To be honest, I really don't know what you are planning, but if you are after a 'sequential' latching of relays (1, then 2, then 3 etc...) you could try a 4017 CMOS decade counter. That only has one output at a time, but the 'order' is fixed (1,2,3...10, then back to 1 again). It just requires a pulse to shift.

Alternatively, a ripple counter, or a shift register (with the input high for the first, then low so you only get a single '1' passing though the shift register).

Considering you only want 'one output on at a time' the 'output' from your digital circuit should be decimal. Now, a binary up/down counter, with binary out, going into a binary to decimal decoder, would allow you to move the outputs up or down.

The reason 'throwaway18' mentioned microcontrollers, is that they can do this sort of thing in spades, and so much more. Plus, they are very cheap nowdays (<1UKP) and easy to program with a homemade circuit and free software. It probably will work out cheaper than using logic IC's (CMOS/TTL) since you only need one IC.

A little more info and I'll see what I can do.

Good Luck



The main post was when I thought you were building this completely from scratch. Assuming you have the kit....

If you have that kit, then I think it can be modified. I think that each relay has a 'latch' circuit, so a pulse turns it on, and another pulse turns it off. What you need to do is have each output (form the RX) reset all other latch circuits. So, output '1' will latch relay 1 on, but rest 2,3 and 4. 2 will latch relay 2 and rest 1,3 and 4 etc... you get the idea. Considering this is all 'logic' it should hurt to just connect wires to all the resets (pin 6 and 8 of the 4013) of the flip-flops. A logic '1' will reset them, jst make sure that the output pins on the RX are 'low' (0-0.5v) when you are not pressing a button on the Tx. So, if you have this kit/board, it'll look a tad messy, you'll need a total of 12 wires (3 extra for each output to reset the other 3).

Thanks for the reply. Just to follow up on it, I will still need operation of all 4 circuts, 1,2,3 and 4. The relays DO need to still latch, although relay 1 would need to shut off when I press button 2, and 2 would need to shut off when I press 1, or 3, or any other of the various buttons. I also need it to operate like said with one button push each time, with as little time as possible during the circut change. So if i press 2, i need 1 to go off almost instantly and 2 to be on, with one single push. Will your idea work like that? and can you please elaborate a bit on how to make that? My skill level still a bit low, so pardon my lack of knowledge. If this works, It will be tottaly awesome. I was nearly about to go build an entire different circut, this will save me boatloads of money.

Correct me if im wrong... Although these ARE dual flip flops, not shure of that matters.

Reciver pin 1, 3 wires to reset 2, 3, 4
Reciver pin 2, 3 wires to reset 1, 3, 4
Reciver pin 3, 3 wires to reset 1, 2, and 4
Reciver pin 4, 3 wires to reset 1, 2, 3

That would defiently make sense to me, because im currently using a relay circut that uses NO/NC in a simular manner to make a push button box. But seince these are dual flip flops, I dont see 4 individual reset pins.

Excuse the MS paint, my pc with my schmatic tools is down right now... The boxes are doides, follow the wire colors to see if im correct. The top for pins represent from left to right 1,2,3,4. The bottom pins represent the 4 resets... also from left to right.

Hi again,

Looks good to me, as I said, so many wires can be messy. There may be one slight problem....because the relays are 'latching', say relay 2 is on, and you hit button 1...using this idea, relay 2 should reset and at the same time, relay one should latch on....but what happens if you hit button 1 again? I think relay one will turn off. (latch-on, latch-off). That way, you'll have no relays latched, until you hit another button.

If you want at least one relay on at all times, then things get a little complicated. That would require you to 'disconnect' the input to the latch circuit when the relay is on, so if the button for that relay is pressed while it is latched, it cannot 'unlatch' it. It can only be reset when another button is pressed. If this is exactly what you want, it can still be done simply.

Btw, I was thinking about just connecting wires to the PCB, good call with the diodes :D That's always a good idea, you might also want to have 'pull-down' resistors on each flip-flop reset, so that it places the resets in a 'known state', saves the relays reseting because of noise.

So, with a few diodes and 4 resistors, it could be soldered on a bit of strip board, with 4 inputs, and 4 outputs (exactly like your lovely MS paint schem :)) It'll make life easier since you only need to solder one wire to each flip-flop reset, and a wire to each Rx output. Less soldering to the board reduces the risk of ruining the PCB.

My skill level still a bit low, so pardon my lack of knowledge. If this works, It will be tottaly awesome

Hey, we are all constantly learning, and this sort of problem solving is a great way to do it, find a problem, analyse it, find a 'simple' solution. It requires less intelligence to come up with a really complicated idea, simple is what we want (cheap, easy to build/modify, and effective in its job).

But seince these are dual flip flops, I dont see 4 individual reset pins

Check page 4.

There are four flip-flops in total, so 2 dual packages. The resets are on pins 6 and 8. Make sure you get the right reset, the schematic (thankfully) is quite clear.

One more thing...the resets are all connected to GND on the PCB. We don't want that. So, you can either bend the pin of the dual flip-flop IC so it doesn't go into the PCB hole and then solder a wire directly to it....or....cut the track that connects it to GND and solder a wire to the pad. For each dual FF, because its a standard logic IC, pin 14 is VCC (+5v) and 7 (bottom right) is GND. The two resets on each IC are on pins 6 and 8, both right next to pin 7. I would say, cut the track between pins 7 and 6, and pins 7 and 8. I small knife should do it. And if you want to connect it back together again, you could just add a 'solder bridge' between the two cut tracks. I might copy the schem from the *.pdf and highlight exactly what needs to be cut/soldered.

Good Luck, and take care,


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