While this is a hot topic and Matt's offer is good, I should check the no-load current draw on the motors I got from the IFM auction. Hard to believe it has been just over a year and I haven't built that bot yet. Too many projects.
If there's a Parallax P2 launch party this fall, I better get crackin'!
Those were the "old style" motors Sir-co. You may have the only 2 known to still be in the wild. (Aside from my private stache here in the pit. Speaking of which...IFM is coming up in a couple months! Getting close for me to clean out our closet here and have another auction for their benefit...ya think?
-MattG
At some point, you will have to consider the PCB's trace widths. They were designed conservatively to handle the stated fuse currents, but there comes a point at ?? amps where the traces themselves will act as their own fuses. I guess the take-away is not to get too ambitious about over-fusing. OTOH, it might be nice to know where the trace-as-fuse threshold actually lies. Are you feeling lucky?
I'm a little late here, as I've been a little busy. I've blown one of the 5 amp motor fuses 3 times now. Each time there was some increased resistance, but the wheel was always able to keep turning up until the fuse blew.
Is it possible I've got a bum motor?
Do you have a way of monitoring the current of the motor?
I often use my bench top power supply to power my robot while I'm testing the code. Like many bench top supplies, mine has a current meter built in.
Another option would be to use a multimeter set to current mode. My Fluke has a 10A socket for use with the amp meter. I think many DMM's have some sort of current meter.
Hey ChrisL8 -
Does it happen to be the right side motor?
PM me your shipping address and we'll get you out a replacement, that should not be happening
-MattG
That way I would be able to properly shut things down in a stall situation, which does happen sometimes in autonomous operation, without having to replace the fuse every time.
I like the idea of the self resetting fuse,
then if I could detect the loss of power at the motor (is there a way to monitor for 12V power with a pin on the Propeller?) I could know when a breaker was tripped and shut down/call for help/etc, while still being able to get going again remotely (i.e. switch to teleoperation and manually navigate out of the situation which caused the stall.)
is there a way to monitor for 12V power with a pin on the Propeller?
Yes, you can use a voltage divider to drop the voltage down to a save level for the PAB's ADC. The PAB uses a 5V ADC so if you battery didn't get higher than 15V you could use this circuit.
*************************************************
Voltage Divider Schematic
*************************************************
15V

│
20KΩ
│
ADC Channel ────┫ << This junction should measure 5V
│
10KΩ
│
 0V
Edit: Darn, the forum software (or my browser) doesn't display the Parallax font correctly now. Hopefully you can still tell what the circuit is.
Building a monitor circuit will also make it easy for me to tell if the "Motor" switch is on or off from the propeller, and to respond to both blown fuses and "emergency kill" situations when someone flips the switch off to stop the robot.
They are supposed to "trip" at over 5amps and then "latch" off until power is removed, so they will not reset until I power cycle the motors, which is exactly what I want. This will require a positive response to any problem before power is restored.
As to whether my motors have problems or not, I'm going to do some more testing and monitoring. It seems that with the rubber wheels the motor can be stalled if the robot is impeded. I thought that the wheel would just slip on a smooth surface, but I think there is enough friction to stall the motor, which ultimately is good. I would rather stall it than burn rubber.
The only down side is it is very difficult to replace fuses, not to mention I don't want to have to buy them in bulk as "robot food".
I will obtain an amp meter though and test to make sure everything is working correctly and compare left to right.
I initially thought I was only blowing fuses on one side, but now I've had it happen on both, so maybe I just need to quit fighting with rocking chairs?
As an update, I got the 5 amp "breakers" and put them between the power supply and the motors,
I also replaced the fuses in the Arlo Power Supply with 7.5 amp fuses, just so that the "breakers" would trip first.
So far I haven't blown a fuse or tripped a breaker since doing that, but I will keep trying and let you know what happens.
I also received the AMP meters, but I haven't put them in line yet. As long as things are working it hasn't been a priority.
Comments
If there's a Parallax P2 launch party this fall, I better get crackin'!
-MattG
-Phil
Is it possible I've got a bum motor?
Do you have a way of monitoring the current of the motor?
I often use my bench top power supply to power my robot while I'm testing the code. Like many bench top supplies, mine has a current meter built in.
Another option would be to use a multimeter set to current mode. My Fluke has a 10A socket for use with the amp meter. I think many DMM's have some sort of current meter.
I'd personally prefer to blow lots of cheap fuses before I ruined my board!
Does it happen to be the right side motor?
PM me your shipping address and we'll get you out a replacement, that should not be happening
-MattG
Here is a question:
Would this be a good idea or a bad one?
"Littelfuse 0UCB005.XP 5 Amp Universal Circuit Breaker"
http://www.amazon.com/Littelfuse-0UCB005-XP-Universal-Circuit-Breaker/dp/B004A8RR3G/ref=pd_sbs_auto_5?ie=UTF8&refRID=0ES8D5EZX6ZGT05AZAZH
Or what about just a real breaker like this?
http://www.amazon.com/Sierra-International-CB41200-Resettable-Circuit/dp/B00144GTHO/ref=sr_1_1?ie=UTF8&qid=1423064713&sr=8-1&keywords=5+amp+resettable+fuse
That way I would be able to properly shut things down in a stall situation, which does happen sometimes in autonomous operation, without having to replace the fuse every time.
I like the idea of the self resetting fuse,
then if I could detect the loss of power at the motor (is there a way to monitor for 12V power with a pin on the Propeller?) I could know when a breaker was tripped and shut down/call for help/etc, while still being able to get going again remotely (i.e. switch to teleoperation and manually navigate out of the situation which caused the stall.)
Thoughts?
Should I start a new thread?
Yes, you can use a voltage divider to drop the voltage down to a save level for the PAB's ADC. The PAB uses a 5V ADC so if you battery didn't get higher than 15V you could use this circuit.
************************************************* Voltage Divider Schematic ************************************************* 15V  │ 20KΩ │ ADC Channel ────┫ << This junction should measure 5V │ 10KΩ │  0VEdit: Darn, the forum software (or my browser) doesn't display the Parallax font correctly now. Hopefully you can still tell what the circuit is.
Building a monitor circuit will also make it easy for me to tell if the "Motor" switch is on or off from the propeller, and to respond to both blown fuses and "emergency kill" situations when someone flips the switch off to stop the robot.
I'm thinking of ordering a couple of these:
http://www.waytekwire.com/item/46859/MINI-CIRCUIT-BREAKER-5-AMP/
They are supposed to "trip" at over 5amps and then "latch" off until power is removed, so they will not reset until I power cycle the motors, which is exactly what I want. This will require a positive response to any problem before power is restored.
As to whether my motors have problems or not, I'm going to do some more testing and monitoring. It seems that with the rubber wheels the motor can be stalled if the robot is impeded. I thought that the wheel would just slip on a smooth surface, but I think there is enough friction to stall the motor, which ultimately is good. I would rather stall it than burn rubber.
The only down side is it is very difficult to replace fuses, not to mention I don't want to have to buy them in bulk as "robot food".
I will obtain an amp meter though and test to make sure everything is working correctly and compare left to right.
I initially thought I was only blowing fuses on one side, but now I've had it happen on both, so maybe I just need to quit fighting with rocking chairs?
Those look very interesting. I hope you let us know how they work.
http://www.hobbyking.com/hobbyking/store/__17864__In_Line_Voltage_and_Amperage_Meter.html
This seems like the most simple and inexpensive way to monitor current draw.
and a couple of these:
http://www.waytekwire.com/wps/myportal/en/products/!ut/p/a1/04_Sj9CPykssy0xPLMnMz0vMAfGjzOJdfSwDPbzdDQ3cA3yNDDy93F3NDB29DQ38DYAKIoEKDHAARwNC-sP1o_AqMTCEKsBjRSTQDeY4TQg2BVpCQEFBboRBlqlFOgClzOxN/#Z7_EL9QHKG10GPM20IJGE61AK10S5
so I will report back on my findings.
I also replaced the fuses in the Arlo Power Supply with 7.5 amp fuses, just so that the "breakers" would trip first.
So far I haven't blown a fuse or tripped a breaker since doing that, but I will keep trying and let you know what happens.
I also received the AMP meters, but I haven't put them in line yet. As long as things are working it hasn't been a priority.
So is that before of after the HB-25s ?
Also what about the fuse on the HB-25s, did you change that ?
Was that fuse not tripping as well ?
Just trying to get feel for what the wiring looks like..
I replaced the fuses in the Arlo Power Supply with 7.5 amp fuses,
So it goes battery->10ampFuse->MotorSwitch->7.5ampFuse->5ampBreaker->25ampFuse->HB-25.
AND, yesterday I had one of the 7.5am fuses blow. I'm not sure how/why that happened. I think the 5amp Breaker should have gone first.
I replaced the 7.5amp Fuse with a 10Amp fuse for now. I'm not sure if that is a good idea or not, but I would like to see the Breaker work.
Thing is that when the motors pull the amps, you want things to trip.
Before it trips the HB25s.
Slow blow or fast blow 7.5A fuse?
How do I tell? I didn't know these mini fuses had the slow/fast blow option.