Boosting voltage from pins due to wire length


I have a project where I am using a Photon to set a pin (momentarily) to HIGH to trigger a camera. The challenge is that the camera is about 25 feet away so the voltage received by the camera becomes too low.

How can I boost the voltage to say 8V or 10V so that I can get at least 4-5v at the camera? I tried voltage step-up regulators but they suffer from an unacceptable delay in boosting the voltage.

Any help is appreciated.

You are looking for a “buffer” and not a step-up regulator.

A simple op-amp in voltage follower configuration would do the job.

THANK YOU @kennethlimcp. I am glad there is a way.

Would you please send me a link as I have no idea what an op-amp is or how it would be connected :-).

Hmm… On second thought, you are only wiring a ground and GPIO pin to the camera?

Or only 1 wire?

I am sending a GND and GPIO.

Without a power source, it’s not possible to locate the buffer IC chip near the destination (camera side) though…

What voltage are you measuring on the GPIO set to HIGH with reference to GND on the camera side?

Trying measuring without connecting to the camera first.

At camera, I am only getting about 1.5VDC (25-foot wire). The camera was not connected.

What did you mean earlier by "…Without a power source, it’s not possible to locate the buffer IC chip near the destination (camera side) )?

Thanks again.

Would something like this work?

Can you measure the GPIO voltage on the Photon side and see if the voltage is indeed 3.3v?

I did. Yes, it is 3.3V.


With wires this length you should consider that these may act as antennas which may even damage your GPIOs when exposed to EM fields.

I plan to use shielded cable or do I need to use something else?

I thought this would be a common problem when the micro is a distance away from a device …?

@Jimmie, what are you driving on the camera side? How much current does it draw? With that much voltage drop, it could be that the camera trigger requires a lot of current. The lower the current, the lower the voltage drop.

You could consider using RS-485 transceivers over twisted pair (eg CAT5) though that would required some power at the camera end.

Thank you @peekay123.

The voltage drop was measured before connecting to the camera.

The camera can handle up to 30V but maximum current is less than 120ma. If you would have the time, here is a link for the camera wiring which is on page 35.

@Jimmie, you can use these RS485 transceivers on both ends though only a transmitter or a receiver will be used in each device:

The unit on the Photon end can be powered from 3V3 and GND and the one on the camera end from the camera’s 3.3v output (red pin 3) and camera GND (brown pin 6). The opto-isolated GND (blue pin 5) is connected to the camera GND.

The camera RS-485 transceiver is set to SEND and the camera side one is set to RECEIVE (easiest to solder the direction pins to GND or Vcc on each RS485 board). The camera receiver output can drive the opto-isolated input (black pin 2) through a 1K resistor (as per FLIR’s table 6.4 values).

Of course, I have never tested this but it should work at distances up to 400 feet. :wink:

Hello @peekay123,

Thank you. I have the following setup for testing, an Arduino UNO as my Photon is in another circuit, and 2 of the following RS485 units connected by a 25 foot cable:

I have programmed the UNO to turn pin 10 to HIGH. I then setup one RS485 for Send (connected DI to Arduino pin) and shorted DE and RE and connected to 5V, and then set the other RS485 to Receive by shorting DE and RE to GND (this end was not connected to camera). Both RS485 units are powered from the Arduino.

Pin 10 is measuring 5V. When the other side of the 25 ft cable is not connected to the “receive” RS485, I am getting 3.0VDC. After that side is connected to the RS485 “receive unit”, I measured close to 5V between GND and R0 however this voltage remains the same whether the Arduino pin is connected or not.

What am I doing incorrectly?

Thanks again in advance.

Hello @peekay123

Can something like this be used?

How would it be wired?

Thanks in advance.

@Jimmie, I assume you are using separate supplies for each Uno/RS485 combination. The RS485 uses a balanced line, non-ground referenced signal so you can’t measure the two raw wires and expect a “normal” voltage. This is why you need the receiver. When you measure the output of the RS485 receiver, you should see 5v relative to the GND of the receiving Uno power supply. The two Uno CANNOT share a common ground.

I suggest you get the first Uno to put out a slow (0.5Hz) square wave and then go measure what comes out of the receiving side. The wave needs to be slow so you can measure it with your voltmeter.

Not even close (the AD623).