It would be cheaper and less power-consuming to use a voltage-divider consisting of 2 resistors to get an input-voltage between 0 and 5V. The next question could be: where to get the power from to run the PSoC. Since a step-down converter has a better efficiency factor than a 78xx voltage-regulator you may consider to use a switching regulator. Have some googles on that theme.
Its not clear what you are trying to do so -
1) A simple diagram would be helpful.
2) Are you tyring to -
a. Power PSOC off a 12 V supply ?
b. Power PSOC with some other supply, and take in 12V and 5 V logic signals
from Receiver into PSOC ?
c. Is receiver relay output a 0, 12V output, or a set of contacts connected to 12 V that
receiver actuates by turning on relay coil
3) You can see a block diagram with labeled voltages would be helpful.
If you are trying to translate a 12 V logic signal to a 5V signal, there are a ton of interface
parts, failrchild semi, ON Semi, that will do that job for pennies. In addition they have single gate
logic translators that will do that. They feature low drive, low power typically, and short circuit protection.
If its a low speed low C interface translation needed then R divider would be fine.
If you are trying to power PSOC from 12V -
1) Linear regulator typically a lot less noisy, so if you are doing precision analog
2) Switcher can have wider input range, in fact there are parts that will buck or boost depending
on input supply, like a battery pack that starts out high (regulator in buck mode) and then drops
below desired Vdd (swicthes over to boost mode).
3) TI, National, Micrel, LT, Phillips are just some of the providers. NSC/TI have an online design
tool to pick and design and evaluate a designs perfromance. Inclduing BOM generation.
thanks for the replies,
Basically I want to interface one of these: http://www.ebay.co.uk/itm/RF-Wireless-Electric-Garage-Gate-Door-Remote-Control-/310412645874?pt=UK_Gadgets&hash=item48460915f2
with an input on my PSoC 1, the output from the receivers relay is 12vdc far too much for an input on the psoc. i was thinking of bringing the 12v signal down to 5v and then using the 5volt as a logic high.
So the voltage divider solution with two "R"s is the easiest.
Then a simple R divider should work. You do have to be concerned
with power sequencing, eg. get PSOC started up first, then GD opener.
If R divider limits total current to < PSOC pin injection current spec you
might be able to get away with powering up both devices at once.
A lot of remotes provides relay contact outputs. ie, Contact close/open during activation.
Check if that is the case, if it is then you don't need the voltage divider.
Hi guys, im not sure if my relay has he microcontroller output, I am still waiting for it to arrive, However I actually have a few of these 5v regulators here now and some capacitors, it would cost me anything to make up a little circuit using the components i suggested, Im short on resistors though. In saying that could I use the setup i suggested. I was also thinking of using a 100uF and a 10uF capacitor instead of the ones listed on the diagram. Speaking of which, is it a good idead to put a filtering/smoothing capacitor across the 5vdc supply connected to ground on the PSoC1 device when i eventually decide to run it on a pcb i make up myself. I was thinking of putting a 0.01uF capacitor across the supply pin and connect it to ground? any ideas, thanks guys
On regulator output you should have both a bulk and a .01 or .1 Ceramic. Bulk handles large
current switching transients, like driving LEDs or large C loads, and the ceramic takes care of
higher freq noise that the high ESR bulk caps cannot. Read your regulator specs, make sure
there is no minimum ESR cap specs on the output that aid in stability management.
thanks for the advice, will try implementing that system
So you received the remote and it is ouputing 12V?
Make I know why you need to use a regulator?
you can use a resistor divider
a resitor in series with a 3.9V zener diode
its just that i dont have any of these zeners about at the moment, id need to order them in. ive made voltage clamps before, i remeber using a 5v7 zener with a diode in series to drop the voltage down to 5vdc, with a resistor value of 100k, not in that order though
No matter what you use, just remember to limit the voltage at the input pin lower then the VCC(VDD).
I would not use a 5V7 zener to clamp the input as the input should less then 5V.
I woudl also measure the output of your reguatlor first and it should always be lower then the VCC of your PSOC
with the 5v7 i wasnt using the said circuit, ive used 4v7's and 100k resistor to provides some protection to inputs and outputs on the psoc but thats about it, I meant to reply to the other query i had before about the programming, i kind of liked the method you were describing but im a little confused about it, i may revisit it soon, just that ive ben busy, also thanks for your replies very helpful