High amp power supply OK for Prop-1?

[BigRez]

I read a couple of other posts that talked about "high current" and wanted to understand that better.   The topics High Current add-on and Looking to do an Elevator Effect both (among others) refer to a connection for high-current devices.  The second thread mentions using a 10A power supply.

The PS that comes with the Prop-1 kit is rated at 1A.  First, can we use a 10A PS (or really something above 1A) with the Prop-1?  If so, what's the max that could safely be used or max recommended to use?  (I do understand that the TIP120 in the link above can handle 5A.)

I understand that about 500mA is available through the OUTx connections, but if using a 10A PS and the high-current add-on as described in the above links, what amps would I be able to draw for a given device? 

(Sorry if this seems basic - maybe I'll enroll in a basic electronics class this summer.  ;D)

[JonnyMac]

Think if it this way: if stuck a soda straw into a swimming pool could you suck it all out?  No, and the pool -- just because it has all that water -- isn't going to force it into you, and there's only so much water you can get through a straw, anyway.  A power supply is the same: it can provide up to X amperes at the rated voltage, but the amps being drawn are controlled by the circuit needing the power, not the power supply.

[BigRez]

Understand. (And I should have because this is just like the PS in computers.  :P )

So to be sure I do, the total amps provided by the PS needs to be at (or probably better to exceed) those drawn by the circuits, the max amps out through the OUTx connections is 500mA (and 1200mA for all of them). If I need more than 500mA through an OUTx connection I need to use the High Current add-on (or something similar) up to about 5A. (Although I thing the docs on the TIP120 says 8A ?) If I need to go 6A or 7A, should I change the TIP120 to something else?

I'm not sure about the PINx connections and how to read the docs.  I read that they supply 5vdc but am not sure what the "sink" and "source" means and what the two group represent. I see per pin at 20mA and 25mA and then the second set listed at 50mA. Is that per the group?

Thanks in advance for your knowledge sharing,

[JonnyMac]

If you need to switch more than 5 amps at 12v it's time to consider a mechanical relay; you could go solid-state (Crydom makes DC relays that will work in the RC-4) but they are VERY expensive.

On the TTL stuff: "Sink" means providing Vss (ground, i.e., the output is low), "source" means providing Vdd (+5v, i.e., the output is high).  We list the specs in the Prop-1/2/SX documentation but keep in mind that on the Prop-1 there is a 220-ohm resistor inline with each output and on the Prop-2/SX there is a 100-ohm resistor inline with each output -- they are there for safety since the processor is an SMD that is not easy to replaced.

[jeffh]

Jon, You mentioned solid state DC relays for the rc-4. Do you sell them? How much?

    I am trying to connect a car horn to the prop1 and there is not enough power to make it work.

We have some 25 amp 12vdc power supplies that I can connect the horn to and make it blow. I do not know the amperage.

Can I connect the 25 amp power supply to the prop1 and connect the horn through a channel or would I damage the prop1 or prop2 controller.

We will be connecting two head lights to a channel also.

[JonnyMac]

No, we don't sell them -- and they are expensive.  For controlling horn you can probably use a standard mechanical relay as you're not going to notice the "click" over the horn and it's not like you're going to be cycling it a lot (right?).

Do not connect the horn directly to the Prop-1/2/SX -- you will blow the ULN right off the board if it needs even 1/10 the current your supply is able to provide.  Same for the headlights; I connected a headlight to a Prop-1 using a TIP120 circuit, but I had to in order to do PWM.  For on-and-off control use a standard relay.