Another prototype PCB ordered

July 23, 2013 in 8 Channel PDU by Joshua Oster-Morris

I just ordered another set of prototype boards. I wanted to have a little more headroom in my current sensors. I can now measure up to 60A per circuit. This will allow me to clamp over current conditions in the analog domain which will happen quite a bit faster than in the digital domain. We will still clamp circuits in the digital domain as well but this feature will better protect the device from high capacity short circuits. The output devices can handle 1400A bursts (yes, one thousand four hundred amperes) but a high capacity short circuit could conceivably produce more current than that and then all bets are off. This change should protect us from that possible outcome. The max current per channel has not been affected by this change. I also added a flash memory chip to the board that could allow the PDU to have it’s firmware updated over the air (OTA). I have not yet committed to that functionality but this flash chip will make it possible should I choose to allow this function. OTA programming while being fantastic for upgrades also means bricking your device is possible. That is a scary proposition, so I need to consider that carefully before I proceed.

pdu rev18OP

Wiring harness update

July 19, 2013 in 8 Channel PDU by Joshua Oster-Morris

We spent some time last weekend working on the wiring harness for the PDU. We like the Anderson connector for the 12V input a lot (the red one). We feel good about the Weatherpack connectors on the outputs (the 2×2 connectors). The input connector, (the 4×1 connector) is really too big for what it does and we plan to replace it with something else. We are looking at our own bikes for ideas, there are a lot of options available. We are looking for something that is easy to get and inexpensive. Those inputs have high input impedance and will carry no current so we cannot think of a reason to use the large 20A plugs there. Likewise the 2×1 connector for the ground and “relay” inputs also carry little current and therefore can and should be shrunk a bit as well.

IMG_9091[1]

One of two output plugs.

IMG_9089[1]

The potted PDU (with the sticker) didn’t get shrink wrapped wire which made it look a messy. Ultimately, we will not be using a potting box for this project. We will have a custom mold made and pot the PDU into an puck with some nifty mechanical features.

IMG_9088[1]

Prototype 3 up and running

July 11, 2013 in 8 Channel PDU by Joshua Oster-Morris

All 8 channels up and running on my new test rig with the new wiring harness. Everything is working as expected. I plan to build up 5 of these this weekend and pot a couple for on the road testing.

8 channels running

My transient generation circuit is pretty badass. >400V Pk-Pk transients.

raw transients

The PDU tames them to something like this.

tamed transients

PDU test platform update

July 6, 2013 in 8 Channel PDU by Joshua Oster-Morris

PDU test platformI just about finished up the PDU test platform today. The only thing left to do is attach the WeatherPak and Anderson connectors to it so I can connect the PDU and begin testing. The connectors have not yet arrived unfortunately so I am in a holding pattern on that detail.

 

 

 

Test rig switchesI will be able to easily pull all the signal inputs high or low with the flick of the switch. I can also short circuit 4 of the outputs to test the circuit breakers (I can test the other 4 rest in software or short circuit them with alligator clips).

 

 

 

removable diodeI’ve put two transient generation circuits on board as well. One of them is directly on an output and will be used to test the device for ruggedness to significant transients directly on the output. I can test it with or without the diode I suggest should be installed across all inductive loads. The other is isolated on its own circuit and can be capacitively coupled to anywhere in the circuit to test durability elsewhere.