Spike Control Line Signals

[Venkatesh]

Hello,

Does anyone know around how much current the control lines on the Spike Relays draw? Also, are they 5V or 12V level pins? I am currently without an IFI control system to get these values, and they would be useful for a project I am working on.

Thanks,

[BrianBSL]

Originally Posted by Venkatesh

Hello,

Does anyone know around how much current the control lines on the Spike Relays draw? Also, are they 5V or 12V level pins? I am currently without an IFI control system to get these values, and they would be useful for a project I am working on.

Thanks,

They are 5V signal level pins, they draw less than 10mA each. When I was hooking up the controls for the BattleCry6 Jeopardy game, I had trouble getting the blue ones to work off of a vex controller, although the red ones worked fine. I ended up using a vex pneumatics transistor driver to run a blue one, because we had an extra laying around and it was exactly what I needed (instead of spending the time to build it). I believe the PIC chips can sink 5mA or so of current, so apparently the blue ones are more than that. According to the post on IFI's website, you can run them off a mini-rc, which should be the same config as a vex controller. Who knows.

Edit:
Accoriding to the FAQ on IFI's site, the full size RC can supply 7mA on each digital out pin, not sure if the Vex controller is different.

[Venkatesh]

Thanks for the info - I plan to use them with a Rabbit Microcontroller (RCM2200) to build version 2 of my HTTP Toaster. Version one required the Rabbit to send a signal to the old FRC Controller, which ran the red relay.

[ConKbot of Doom]

A PIC can source or sink 20 mA typically, and sink 25 mA in some chips. However there are power restrictions on ports and the power pins, so you aren't going to be using all the power on all the pins at the same time. Plus IFI probably has some isolation/protection circutry to keep from hosing the PIC with static or by accidentaly sending it 12v or something. That probably has more to do with the current limit then the PIC its self.

[Andy A.]

The only diffrence between a Red (old) and Blue (spike) is that the blue version has reverse polarity protection on the battery supply terminals.

Red versions will fry quite nicely if exposed to reverse current. Blue's won't.

-Andy A.

[sanddrag]

We used spikes in the 2005 kit to fire our double solenoid valves. But when triggered, they would osillate back and forth very rapidly. When we switched to older spikes (don't remember if they were red or blue) everything was totally fine.

The 2005 spikes look like they have a larger case than the older ones.

[Andrew Blair]

Originally Posted by sanddrag

We used spikes in the 2005 kit to fire our double solenoid valves. But when triggered, they would osillate back and forth very rapidly. When we switched to older spikes (don't remember if they were red or blue) everything was totally fine.

The 2005 spikes look like they have a larger case than the older ones.

Tell me about it! Using them on our new remote control go-cart of death we encountered the same problem. Somehow we got one to work, though we couldn't get another to work and had to switch to an older blue spike. Perhaps this was the result of the reverse polarity protection? That would make me feel dumb....

[BrianBSL]

Originally Posted by Andy A.

The only diffrence between a Red (old) and Blue (spike) is that the blue version has reverse polarity protection on the battery supply terminals.

Red versions will fry quite nicely if exposed to reverse current. Blue's won't.

-Andy A.

I know that is the only effective difference that IFI states, however try it for yourself with a vex controller. I tried several (5 or so) different blue spikes from various years, including this year's ones in the new cases and previous years, and had the same problem with both, whereas the 2 red spikes i had worked fine, hooked up to the same 12V lines and the signal cable from the vex controller.

[Andy A.]

I can only speculate as to why there is a (apparent) difference between the two flavors of spike. My best guess is that the reverse current protection is in the form of an optical isolation control system, at least in part.

An optical isolation system is pretty simple. Instead of the control signals effecting the Spikes circuitry directly, the signal operates a internal LED opposite of a photo sensor (or equivalent sensor). The sensor 'reads' the LED, and translates it into what ever state the Spike should be in. It's like putting a little remote control in the Spike. In this way, the RC is never directly connected to, or risks being connected to the robots main power. This is good from a safety standpoint and it cuts down on interference. It might also keep the delicate control electronics isolated from reverse current, although I would guess thats not the only protection used.

In any case, I don't know if the Reds were also opti-isolated. But, since the Reds and Blues are, according to IFI, interchangeable I'm guessing that regardless of the presence or lack of opti isolation, the control signal is the same, including power consumption.

Also, the '05 spikes look quite different then every other version I've seen. But, since opening a spike isn't something I've managed to do (I've tried!), I couldn't say what has changed inside. Probably little, if anything.

So why the apparent difference in performance between the colors? I can't say for sure. On paper, there isn't one. The opti-isolation theory strikes me as being pretty weak. Perhaps someone who knows a bit more about the inner workings of a spike could chime in with some ideas. If no one has the answer, this should probably be raised with IFI. It's kinda scary having 3 different control systems from IFI, and legacy Spikes that may or may not work on some systems. Makes me wonder about what else could crop up.


-Andy A.

[Venkatesh]

I just borrowed a 2002 Blue Spike and measured the current required to switch the relay forward at 5.5V (supply issues). I found that the spike needed 85 mA to switch, which is way out of line with anyone's measurements from here. I also found that just powering the spike required 42 mA. I don't think the IFI controller is using just the PIC to drive the relays, but instead probably a number of relay drivers.

I checked the numbers many times. Any ideas?

[BrianBSL]

Originally Posted by Venkatesh

I just borrowed a 2002 Blue Spike and measured the current required to switch the relay forward at 5.5V (supply issues). I found that the spike needed 85 mA to switch, which is way out of line with anyone's measurements from here. I also found that just powering the spike required 42 mA. I don't think the IFI controller is using just the PIC to drive the relays, but instead probably a number of relay drivers.

I checked the numbers many times. Any ideas?

Wow. Those numbers sound almost as if the control lines are directly driving the coil. I guess I always thought that it was a 12v coil relay with a transistor to trigger it on and off with 5v.

[Al Skierkiewicz]

Venkatesh,
The Spikes I have opened use an optocoupler for control interface. I would suspect that they are designed for a 20 ma loop (standard interface) for control. So the 85 ma make me think something is wrong.(either metering or control) Remember that Spikes do not use a PWM input, they are fed from the relay outputs of the RC. The optocouplers inturn feed into switching transistors that control the relays. Relay power comes from the power input (+12v). There are the standard complement of clamp diodes across the relays and steering diodes for reverse current protection. I thought the major difference between red and blue was that the red output leads were not independent. (That is why you had to add steering diodes to a dual solenoid control for red spikes) In the blues you can have both go high, both go low or one high and one low. The default for blue is both lines are low with no input.