Let's Make Robots!

SRF005 blinking all the time?

I am using a Picaxe 28x1 board and I have connected a SRF05 as shown here.

http://letsmakerobots.com/node/66 .

 My problem is that the little Red LED on the SRF-005 is blinking constantly as soon as i tell my motors to go any direction. 

I have tried to force the port 3 low before and after the commands that makes my motors turn, but it makes no difference.


Is this a common problem? Have anybody else experienced anything similar? 

Any input is appreciated.

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AHAA! It seems to be a problem with the motors. When the motors can rotate "freely" the red LED on the SRF-05 stops blinking and my servo jitter reduces.

How could I fix this?

a) Changing to lower geared motors? For the moment I am using  1:120, but I also have 1:200. (I am using rubber threads)


b) Putting a caps in parallel with the motors? What would be a good cap for something like this? :S ?



What is your power supply configuration? I looks to me that possibly your MCU is constantly resetting while your motors start to eat power higher rhan freewheeling. If you use single power supply, I advise to use 2nd one for motors, servo, etc. Picaxe 28 pin board manual has explanation how to hook it up.

Thank you! I will try that!

 Now to buy some battery holders before the shop closes... :D

Another trick is to put a larger cap (~100uF is usually a good choice for smallish bots) across the power terminals from the battery pack that supplies the motors, or any other high-current devices.
The cap charges up when the current draw is low, but when the motors pull a higher current than the batteries can provide the cap dumps its stored charge back into the circuit, providing an extra boost as needed. Larger caps will give a more sustained boost, but take longer to charge and take up more circuit space. If the cap is big enough to cover the extra current surge then not only do the motors get more power when they need it, but it prevents the supply voltage dropping so much, which seems to be what is causing the SRF005 to reset.

I have tried everything... Well much.  Putting a cap (80uF) across the battery pack, playing around with the code, Using two power supplies (2 x (4 x 1,2 V)) , changing to lower geared motors (1:200), used a toothbrush to ensure that there is no small metal-cables ore scrap on the board to cause shorts. I don't know what caused this but for the moment the interference is tolerable.

 When I have my serial 16*2 LCD connected it gets some interference to.

  Here is a video of the  problem in action:



Hmmm... Unfortunately cannot watch video at the moment. Maybe a stupid question to ask, but are you using correct set of holes on SRF005? The other set is for calibration purposes and should not be used. If I remember right the proper set is on opposite side from red LED.

It is working properly. It returns the range as it is supposed to do.

 I don't have two sets of holes on my SRF-005 !!??, but I am using the ones on the opposite side of the LED. 

I ordered it from here:

  Ghosts in the machine? :)