# giving a toggle switch memory?...

A

Jan 1, 1970
0
I've got a radio with a bass boost toggle switch on it but it always
resets to "off" when the power is reset. I assume its some kind of
standard electronic toogle switch arrangement. An LED comes on when
the switch is "on".

I thought about simply wiring the switch permanently closed (would be
like someone holding the switch down all the time) but would this have
an adverse effect on the rest of the electronics?

What can I do to make this switch have power independent memory? Can
I wire up a latching relay in parallel with a kind of feeback so that
when the switch is pressed it closes the circuit? Then when the radio
is powered up again the circuit would already be closed. Pressing the
switch again would (hopefully) open the latching relay.

Would one of these
http://www.maplin.co.uk/products/module.asp?CartID=040405132749521&moduleno=20476

do the job or do I also need to circuit to figure out the toggling??

Thanks I'm a bit of a novice when it comes to things like this!!

Steve

S

#### soundman

Jan 1, 1970
0
I've got a radio with a bass boost toggle switch on it but it always
resets to "off" when the power is reset. I assume its some kind of
standard electronic toogle switch arrangement. An LED comes on when
the switch is "on".

I thought about simply wiring the switch permanently closed (would be
like someone holding the switch down all the time) but would this have
an adverse effect on the rest of the electronics?

What can I do to make this switch have power independent memory? Can
I wire up a latching relay in parallel with a kind of feeback so that
when the switch is pressed it closes the circuit? Then when the radio
is powered up again the circuit would already be closed. Pressing the
switch again would (hopefully) open the latching relay.

Would one of these
http://www.maplin.co.uk/products/module.asp?CartID=040405132749521&moduleno=
20476

do the job or do I also need to circuit to figure out the toggling??

Thanks I'm a bit of a novice when it comes to things like this!!

Steve

the switch you are using is a pushbutton that is only closed when you have
your finger on it. The whole of its function is controlled by an controller
inside the radio and therefore, the ideas you mention probably won't work.

You can try:

shorting the contacts on the switch so that when the radio turns on if will
set the bass boost on - this will work as long as the controller doesn't
look for the switch being open crcuit first.. It may work, it may not.

Or, if that doesn't work, you will need to make a small circuit that will
pause after power up, close a relay contact for a second and then open
again. This will simulate the manual action. If you are able to use PICs,
one of these will do the job for you with just a few minutes of programming

Plus about $100.00 for the development system. S #### soundman Jan 1, 1970 0 Rich Grise said: Plus about$100.00 for the development system.
You are quite right if he decides to go to a Microchip development system
but there are less expensive solutions. The cheap and cheerful hobby
programmers limit the user to certain types of PIC, but that won't be a
problem in this case. Any PIC will do the job and as this is such a simple
application, it is quite possible that a new PIC user can gain the skills to
do this very quickly. Perhaps as an alternative, someone might be able to
knock out a PIC for him. That relieves him of the investment and still
provides a quick solution for him with a minimum of components.

In fact, as Steve, the original poster, is UK based, I could probably help
out and send him a PIC if he wants to use it. I happen to have small
circuit boards that will support a PIC and a relay driver, so Steve, if you
want one, contact me by email and I'll post one to you.
[email protected]

The cost of a programmer is often mentioned as a barrier to the use of
microcontrollers, but most people who ask questions here are willing to
invest some time and money to get a solution to their problem or to develop
skills. Whatever technology is selected for a project, there is normally a
need for a set of hand tools, soldering iron and a meter which can very
quickly reach the same cost as a programmer. While many people will already
have at least some of those tools, it isn't unreasonable to consider
investing in a programmer if they are planning to take on more projects in
the future.

Having said that, I also understand that for a one off project, the
financial investment and the initial learning may prove to be a real
barrier. There are normally other solutions and I would never suggest that
microcontrollers are the only way to go or that they provide a better
solution in every case. Personally, I use them frequently because the
range of work I do means that I can use them as timers, drivers, logic
replacements, serial drivers and analogue comparators among other things.
Using these means that PCB layouts are often identical for different
applications and new PCBs will normally be variations on existing layouts.
Despite my preferences, I am concious that even if they suit me, that is no
indication that they will suit others or their design methods. I am always
fascinated to see alternative methods and I never fail to be surprised at
the range of solutions to a simple problem.

Peter

A

Jan 1, 1970
0
soundman said:
In fact, as Steve, the original poster, is UK based, I could probably help
out and send him a PIC if he wants to use it. I happen to have small
circuit boards that will support a PIC and a relay driver, so Steve, if you
want one, contact me by email and I'll post one to you.
[email protected]

Hi Peter, thanks! I'll get in touch by email once I've figured out a
few things.

This is a car radio. I was thinking about hooking up a couple of 555
timers to the power feed so that when the thing is switched on there's
a momentary delay then a pulse to a relay which would mimick the
button being pressed. This would give me "on by default" but doesn't
address the "memory" problem. It'd be nice to have the switch
remember the last state it was in. I was thinking about using a
latching relay to enable/disable the pulse on power up. This is what I
have to think about a bit more. I have a basic understanding of
electronics but haven't really done any since school days!

I know this isn't a bit deal but it's quite an interesting problem,
for me at least.

Steve

S

#### Seth Koster

Jan 1, 1970
0
Since the base boost light is a handy reference, why dont you use it
as an inverted trigger for the 555? That way if the light is off,
the 555 triggers. If you AND the radio on reference with the NOT
bass boost light you should get usable logic which waits until the
radio is on and the bass boost is off before attempting to trigger.
You might want to clock the logic so you dont have to worry about the
circuit oscillating from delays in the radio circuit (IE the 555
triggers, but before the radio processes the request and turns on the
bass boost light the logic triggers the 555 again, turning off the
bass boost, etc.).
If you really want memory, you could use a couple flip flops,
feeding them with logic from your references/inputs and then run your
logic from them to the 555, but I'm not sure exactly what you want the
memory to do. Either way, I'd tend to go with discrete components
instead of a processor, but thats probably because I'm more familiar
with them. This doesnt seem like a problem which would need that
much logic (two bits would tell you everything you need to know,
regardless of what you need to do with that information).

A

Jan 1, 1970
0
If you really want memory, you could use a couple flip flops,
feeding them with logic from your references/inputs and then run your
logic from them to the 555, but I'm not sure exactly what you want the
memory to do.

Problem is this..
The bass boost is off by default and is reset by power off/on.
I want
* At least boost on by default (at power up)
* but preferably the last state before power off/on to be memorised
i.e. if the boost was off before power off it'll be off next time it's
powered on & if the boost was on it'll be on next time.

S

#### Seth Koster

Jan 1, 1970
0
Problem is this..
The bass boost is off by default and is reset by power off/on.
I want
* At least boost on by default (at power up)
* but preferably the last state before power off/on to be memorised
i.e. if the boost was off before power off it'll be off next time it's
powered on & if the boost was on it'll be on next time.

Bass boost on = A
Power on = B
New switch on = C

My last posting on this subject should handle your first possible
solution (bass boost at power up). To save the state you could use a
flip flop which is powered all the time. An easier way, if you dont
input AND gate A' B C, and B C' into another AND gate, resulting in
this logic: A'BC = on, BC' = off. Now the switch should control the
bass boost directly, with it coming on anytime the radio is on and the
switch is on and going off if the switch is off and the radio is off.
The positive aspect of this over the flip flops is that the state is
saved in the switch and therefore requires no constant power (I
believe you said this was in a car?).

S

#### Seth Koster

Jan 1, 1970
0

Bass boost on if power and switch are both on and bass boost off if
power is on and switch is off.

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