Official Forum

JCM inVentures Inc.

(403) 284-2876


Troubleshooting QueenAnts...

QueenAnt Version 1

The first thing we must determine is exactly which version of the QueenAnt you have... The very first versions of the QA ( QueenAnt ) had no potentiometer on the front.  This made it difficult for the robot to be sensitive to light so a potentiometer was added to the very front of the robot to help adjust sensitivity.  If you have this early version, then you should ask us for a potentiometer upgrade kit.

QueenAnt Version 2

This second version of the QueenAnt had the potentiometer installed.  We later added in a two colour LED and capacitor to the drone board to make it easier to adjust the sensitivity of the robots phototropism to the point that the robot could follow a dark line on a light surface!  If you do not have the two colour LED and capacitor, then contact us, and we'll send you one.

Troubleshooting steps...

Visual Examination...

  1. Check all components for correct polarity.  Diodes, transistors, IC's, and electrolytic capacitors all have a polarity which must be adhered to. 

  2. Check your soldering very carefully (use a magnifying glass if necessary )... this is the prime cause of failure of robot kits like this.  Look for...
    1. Too much solder which forms a ball
    2. Too little solder which does not fill the pad completely
    3. Solder shorts between two pads
    4. long wires protruding from the bottom of the board which might short against a neighbor.

Madlabs has a great page for checking the quality of your work over here.

Check that all components are in the correct location.


Here is the schematic for the QueenAnt main board...

First thing we have to do is determine where the problem is... the power supply, the motor control, the light sensor, or the drone board...

Step 1:  Testing the power supply

Connect the battery ( make sure it is fresh! )

Remove the Enable jumper J2

If the red LED at the rear of the robot lights up, then the power circuitry is working.

Step 2:  Testing the motor controller. 

Remove the drone board from the main board

Using a length of solid insulated wire, connect the following on the main boards 14 pin header

Pin 14 sidePin 1 side



Pin 1 to Pin 9, pin 2 to 10 ...  connect power jumper J1 briefly.  Right motor should go fwd.


Pin 2 to pin 9, pin 1 to pin10...Connect jumper J1 briefly.  Right motor should go backward.


Pin 1 to pin 7, pin 2 to pin 8... Connect J1 briefly.  Left motor should go fwd.


Pin 2 to pin 7, pin 1 to pin 8... Connect J1 briefly.  Left motor should go backward

If the motors behaved as described, then your motor h-bridge section at the rear of the QueenAnt is working well.  Disconnect power jumper J1


Step 3:  Testing the Light Sensors

You'll need a red LED for this test.  Remove the motor enable jumper J2.  Put on the power jumper J1.  Center the adjustment potentiometer.  Make sure the feelers are centered through the feeler loops ( not touching the loops )


Place the RED led into the 14 pin socket on the mainboard , negative to pin 11, positive to pin 12.


Temporarily short out the two leads of CdS 2 ( right CdS eye )  Led should come ON ( if it's not already. )


Remove the short and hold the robots right eye to a bright light source... Led should come ON.


Reverse the LED so the negative lead is in pin 12 and the positive in pin 11.


Short out the left CdS photocell with a piece of wire.  Led should come on.


Remove the shorting wire for a moment and hold the robots left eye to a light.  Led should come ON.

If the LED's have come on correctly, then the op-amp "U1", CdS photocells, and the rest of the sensor circuits are working fine!

Step 4:  Testing the feelers. 

Make sure the feeler wires are passing directly through the feeler loops.  Remove the jumper from the enable lead J2.  Connect the jumper plug to J1 to power the QA. 


Connect the negative lead of an LED to pin 2 of the 14 pin header.  Connect the other LED lead to pin 14.   You should see a very faint light on the LED.  Touch the right feeler to the loop and the light should go out.


Move the LED lead in pin 14 to pin 13.  You should see a  very faint light on the LED.  Touch the left feeler wire to the sensor loop and the light should go out.

If the circuit behaves as described, then the feeler circuitry is working correctly. 

Disconnect power jumper J1

Step 5:  Testing the drone board...

Here is a link to the drone board schematic...

If all the above tests prove those sub-systems are ok, then your problem is most likely your drone add-on board. 

You'll need a Voltmeter for this test...  All voltages are less than 10Vdc.

Place the power jumper J1 on.  Place the motor enable jumper J2 on.  You might like to bend the motor brackets up slightly so your motors do not contact the table and allow your patient to run away! 

J4 and J5 on the Drone board should be to the right. ( Phototropic )

Rotate Potentiometer entirely Counterclockwise ( viewed from the front ).  Right motor should spin forward in a working QueenAnt.

For the following measurements, any voltage greater than 2.0V is a logic HIGH, any voltage less than 1.0V is a logic LOW.  ( All voltages with respect to ground , pin 7 )  If you have access to a logic probe, this would be ideal.  If not, use the voltmeter and do your best


Pins 1,2 should be logic low, pin 3=high


Pins 4,5 should be low, pin 6 = high


Pin 12=low,  pin 13= high, pin 11=high


Pin 9=high, pin 10=high, pin 8=low

Now rotate the potentiometer entirely Clockwise ( viewed from the front )  Left motor should spin forward in a working QueenAnt.


Pins 1,2 should be logic low, pin 3=high


Pins 4,5 should be high, pin 6 = low


Pin 12 = high, pin 13 = high, pin 11 = low


Pin 9 = low , pin 10 = high, pin 8 = high

Now measure the following pins while touching the left or right feelers to test those responses.


Feelers not touching sensor loops:  both pin 13 and 10 high


Left feeler touching sensor loop:  pin 13 low,  pin 10 high


Right feeler touching sensor loop:  pin 13 high, pin 10 low

If these measurements are correct, then your drone board logic seems to be fine.


This troubleshooting should help you isolate your fault an area of the circuit board.  If you still can't locate the trouble, please contact us at and let us know your results.