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Dotnet

Member
Hello,

Further to a recent post I need a little help on the included schematic


What I'm trying to do is only use the battery when a key is pressed on a remote control.

I am restricted to using a bespoke handheld unit which is fed via an A23 12V battery. I am using a combined RF transmitter and encoder with a Vmax = 6V.

Other than perhaps a delay on the "Power-On" pin of the regulator should the design work? I would like to get rid of some resistor if possible.

Any thought

Thanks in advance
Matt
 

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Diver300

Well-Known Member
Most Helpful Member
You could reduce the 100k resistors feeding the diodes a lot, and put a big capacitor from the regulator enable to ground, in parallel with the unlabled resistor.

That will keep the power on for some time after the buttons are released.

If it is a remote control, it is unlikely to be used a lot. A switch mode converter will make it use a lot less power, but only when the button is pressed. Most of the power used comes from what it used in standby, and a switch mode converter won't help at all in standby.

I would also suggest that you run the transmitter from 5 V. It will use more current on 5 V, but it will also transmit much more power. According to the data sheet, going from 3.3 to 5 V increased the current from about 3.8 to 5.5 mA (1.45 times) but the power goes up from +4.8 to +8 dBm, so by +3.2 dB or just over 2 times.

The extra power will make the users have to press the buttons less, so can save overall battery use.
 

duffy

Well-Known Member
Yeah, you may not even need those four 100k resistors leading to the diodes. Adding a cap is an excellent idea, so's boosting the output voltage. What's the part number on "reg"?
 
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Dotnet

Member
Thanks both for the reply.

Just to give you a bit of background I am increasing the range and number of channels for an RF remote control unit for a disabled person. The problem is due to their physical disability I have to use their existing unit which has been custom designed (at greatcost) and adapt it for my needs. This nessitates carfeful consideration for the physical component size etc etc and hopeing to get a far superior battery that is available pesently.

I agree with putting a cap in to extend the output time, but was concerned that the wrong value CR would delay the voltage 'appearing' at the ouput and consequently to the rest of the circuit so the switxh encoding would be lost. Basically I wanted the user to keep the button pressed long enough to allow the debounce and tranmission of data, no good just quickly touching a button initiating the circuit and tranmitting no data.

Resistors connected to the diodes - fair point !!!!

I was considering a switch converter (ref other post) before it occured to me to only energise the circuit when needed - and that is where we are at the moment just seeing if my initial CCT idea was valid.


Any way will the principle work or am I missing something?

The items I have sourced are

Regulator Seiko S-182C (Low Drop Out) 1uA standby current, Max Vin 18Vdc
Transmitter Link Technologies TXE-433-KH2 (worst case 3mA neeed for transmission)
Antenna Link Technologies 'Splatch'
Transistor Intersil HFA3046B
Package (5)

Matt
 

duffy

Well-Known Member
Any way will the principle work or am I missing something?
What, your switch circuit? Electrically it should work great (assuming the remote doesn't used a matrixed keypad). I checked the S-182C spec sheet for Von/off and it works fine connected to Vin without the resistors.

Software-wise, I'm afraid it's a little more of a crap shoot. Need to know more about this thing you're trying to drive. I contacted the manufacturer, Bespoke, and they said they get calls like that all the time, it's a quirk of the language. Have you tried powering up the unit while holding one of the buttons down?
 

Dotnet

Member
Hi Duffy

Thanks for the input


Yeah All I want to do is use the 12V battery voltage to switch on the rest of the circuit which comprises a <=6V device (KH2).

Now I realise its a bit of a hammer - nutcracker situation but my background is digital not analogue so I have to buy in RF Tx modules to make up for my lack of knowledge and this unit comprises relatively low size with an included tranmitter but is 6V max . I was going to use a Holtek 12E but couldn't find an RF module to physically fit in the case.

The other end of the link will be mains rated relays and digital lighting/dimming control

Your software comment confused didn't mention SW and I'm not using it.

For a matter of interest - which manufacture did you contact and what question(s) did you
ask

If you are referringto the resistors on the diodes I agree - to make a diagram for the post I quickly copied my initial pencil which happened to include the resistors. If you are referring to the resistor on the PowerON/OFF line I just included it purely as a pull down resistor to make sure the thing turned off and not use battery voltage when not required.

Matt
 
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duffy

Well-Known Member
Keep that pull-down resistor. The software I was referring to is burned into the TXE-433-KH2 controller, you are going to have to try one to determine if it locks out a stuck switch on power-up.

"Bespoke" is one of those terms I wish you guys would stop using. I don't mind if you ask me if I'm queer when I'm sick, but this one always sends me to a search engine looking for their company's web page.
 

Dotnet

Member
Hi Duffy,

I don't think the KH2 does lock-out on power up - it will just transmit the key pressed.

Bespoke whats the matter with bespoke??? generic term generally used for a one of design

By the way queer - a 1940 term generally used by grandmothers for feeling 'a bit odd' (later revised to mean gay (homosexual not happy) now no longer used thank God!!!

Resister - I am

Again - who did you contact -I'm curious

Matt
 
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