CDM1550LS+ has me stumped

[redneck_1086]

I am setting up my CDM1550LS+ to turn on my emergency lights in my vehicle, along with radio rebroadcast. (P2 short press turns warning lights on, P2 long press turns radio rebroadcast on).

The problem is the rebroadcast relays works on pin 4 but the lights relay does not work on pin 8. Am I missing something somewhere?
I have it set to pull to go to ground.

[SteveC0625]

I am setting up my CDM1550LS+ to turn on my emergency lights in my vehicle, along with radio rebroadcast. (P2 short press turns warning lights on, P2 long press turns radio rebroadcast on).

The problem is the rebroadcast relays works on pin 4 but the lights relay does not work on pin 8. Am I missing something somewhere?
I have it set to pull to go to ground.

What functions do you have programmed to pins 4 and 8 and how are you triggering those functions in the CPS?

And what functions do you have assigned to P2 short and P2 long?

Without detailed info on how you've got it set up so far, it's a bit tough to offer a fix.

[redneck_1086]

I've got pin 4 programmed for Auxiliary Control 2, and pin 8 programmed for Auxiliary Control 1.

These are triggered via button P2

Sorry I didn't provide more info, I've done this before but this one has me stumped because one function works and the other doesn't. I unplugged the 20 pin connector and grounded where pin 8 goes and it tripped the relay so I know its on the radio side.

[RFguy]

What size/type relay are you using on Pin 8?. I seem to recall that the CDM's can only drive low-current logic devices on pin 8. Standard relays draw too much current.

Pin 4 has a higher current drive transistor as it was designed for horn output (legacy) so can direct drive a standard relay.

Try measuring the voltage on pin 8 without your relay attached. It should be 5-volts and switch to zero volts when active. This will confirm the pin is programmed correctly.

[redneck_1086]

Hmmmm, that makes sense. I think all of my other projects I have just used pin 4.

These are the relays I am using
http://www.delcity.net/store/Relay-with-Diode/p_73578

How should I work around this?

[SteveC0625]

Yup, we lost a transistor that controlled one of the acc. pins on a CDM1250 to the same cause; too much current draw to trip the relay.

From the Detailed Service Manual: DIG IN OUT 4,7,8 are bi-directional and use the same circuit configuration. Each port uses an output transistor Q0177, Q0183, Q0185 controlled by μP pins 46, 47, 53. The ports are read by μP pins 75, 54, 76. To use one of the ports as input the μP must turn off the corresponding output transistor.

Pin 4 is indicated to be used for External Alarm which would give us a good idea why it can drive a relay where Pin 8 can not.

[redneck_1086]

It says Pins 4,7, and 8 use the same circuit configuration? Wouldn't that mean it should work? What would make this possible if it dosnt? another transistor?

[SteveC0625]

It says Pins 4,7, and 8 use the same circuit configuration? Wouldn't that mean it should work? What would make this possible if it dosnt? another transistor?

According to the schematic I am looking at, Pin 4 controls or is controlling A+ while Pin 8 uses 5v. That might account for the difference in how the two pins deal with the relays.

I searched all through the manual and could not find anything further on Pins 4 and 8.

[redneck_1086]

what about pin 12? it also shows the option for Auxiliary Control

[SteveC0625]

what about pin 12? it also shows the option for Auxiliary Control

I don't have the manual open now, but only Pin 4 had the A+ on it. All the others were 5v including 12.

[redneck_1086]

Would a transistor work if the base was tied to Pin 8, the emitter tied to ground, and the collector tied to the ground of the relay coil?

[redneck_1086]

I tried this with at 10k resistor on the base and it is working....but is it safe for the equipment?

[RFguy]

You could get away with no resistor and put pin 8 stright to the base (but I would use a 1k for isolation). There is an internal 4.7K resistor that pulls high to 5 volts when pin 8 is high. It's that internal 4.7k that is in series with the base of your transistor.

I can e-mail you that page of the schematic if you like.