I would like to power my KFlop with a separate 5VDC power supply,
separating it from USB power and allowing for more current for external
circuitry. Due to my present layout restrictions I cannot easily apply
power to connector JR1. Is it possible for me to safely apply my 5V
external power to another connector such as one of the JP-type IDC
connectors?

sam marrocco | chief technical officer
ringside.cutters.flavor.picnic.moonlink

248 548 2500 w
248 910 3344 c

ringsidecreative.com

<http://ringsidecreative.com/>

 

Hi Sam,

+5V power can be applied at the other connectors. The IDC pins are rated for 1Amp. If using ribbon cable try to use 26AWG ribbon cable rather than the more common 28AWG. Use multiple pins where they are available. Keep wiring as short as possible. Consider using the KFLOP GND lug for +5V ground. 

Tom,
I have applied +5VDC to pin 23 of JP7 and am using pin 25 as ground. I have no USB or anything else connected to the KFlop. I have removed jumper J3. I have also tried pins 24 and 26 to power and gnd respectively.

I get no leds on the KFlop. I'm certain the 5VDC power supply is working well and good for 900 ma.

If I connect the USB to the computer and add Jumper J3, the board works fine.

Am I missing something here in order to power the board from the IDC pins?



sam marrocco | chief technical officer
ringside.cutters.flavor.picnic.moonlink

248 548 2500 w
248 910 3344 c

ringsidecreative.com

Hi Sam,

What you describe should work.  Are you counting pins from the right end?  Take great care as applying power to the wrong pins is likely to cause damage.

You can check with an ohm meter for simple copper continuity from those pins to the molex connections.

Regards

TK

 

On 1/23/2017 9:19 AM, Tom Kerekes tk@... [DynoMotion] wrote:

 

Hi Sam,

+5V power can be applied at the other connectors. The IDC pins are rated for 1Amp. If using ribbon cable try to use 26AWG ribbon cable rather than the more common 28AWG. Use multiple pins where they are available. Keep wiring as short as possible. Consider using the KFLOP GND lug for +5V ground. 

Tom,
I have applied +5VDC to pin 23 of JP7 and am using pin 25 as ground. I have no USB or anything else connected to the KFlop. I have removed jumper J3. I have also tried pins 24 and 26 to power and gnd respectively.

I get no leds on the KFlop. I'm certain the 5VDC power supply is working well and good for 900 ma.

If I connect the USB to the computer and add Jumper J3, the board works fine.

Am I missing something here in order to power the board from the IDC pins?



sam marrocco | chief technical officer
ringside.cutters.flavor.picnic.moonlink

248 548 2500 w
248 910 3344 c

ringsidecreative.com

 

Hi Sam,

What you describe should work.  Are you counting pins from the right end?  Take great care as applying power to the wrong pins is likely to cause damage.

You can check with an ohm meter for simple copper continuity from those pins to the molex connections.

Yep, correct end....and continuity checks out.

External power is a stable 12volt supply feeding a 7805-series 5 volt regulator. External circuitry (a couple of simple Schmitt triggers and optoisolators) works fine, but when the KFlop is added to the system it won't boot even though nothing else is connected to the KFlop but power. I tried different external 5vdc supply and it works. But none of my internal 7805 regulators, even with all circuitry removed except the KFlop, will work. I'm guessing I ended up with some bad 7805s that can't handle the (relatively) meager current draw of the KFlop. As soon as the KFlop is connected the otherwise stable 5v output of the 7805 shows some slight fluctuations every second or two. I'll have to try some alternate power supply solutions.....thanks for the tip.

sam marrocco | chief technical officer
ringside.cutters.flavor.picnic.moonlink

248 548 2500 w
248 910 3344 c

ringsidecreative.com

Hi Sam,

Do you have filter capacitors close to the 7805 so it doesn't go unstable and oscillate?

Regards

TK

 

On 1/27/2017 1:58 PM, Tom Kerekes tk@... [DynoMotion] wrote:

 

Hi Sam,

What you describe should work.  Are you counting pins from the right end?  Take great care as applying power to the wrong pins is likely to cause damage.

You can check with an ohm meter for simple copper continuity from those pins to the molex connections.

Yep, correct end....and continuity checks out.

External power is a stable 12volt supply feeding a 7805-series 5 volt regulator. External circuitry (a couple of simple Schmitt triggers and optoisolators) works fine, but when the KFlop is added to the system it won't boot even though nothing else is connected to the KFlop but power. I tried different external 5vdc supply and it works. But none of my internal 7805 regulators, even with all circuitry removed except the KFlop, will work. I'm guessing I ended up with some bad 7805s that can't handle the (relatively) meager current draw of the KFlop. As soon as the KFlop is connected the otherwise stable 5v output of the 7805 shows some slight fluctuations every second or two. I'll have to try some alternate power supply solutions.....thanks for the tip.

sam marrocco | chief technical officer
ringside.cutters.flavor.picnic.moonlink

248 548 2500 w
248 910 3344 c

ringsidecreative.com

 

Hi Sam,

Do you have filter capacitors close to the 7805 so it doesn't go unstable and oscillate?

Yes, on both the input and output.
It looks as though I have a batch of bad 7805s. This batch was purchased from China, and 3 out of 5 seem to have the problem. It was introducing some oscillation at around .5 hz. Very odd. Switching to a different batch of 7805 chips seems to have alleviated the problem. One more item to add to my list of things to NOT buy from China (along with measurement gages and micrometers).

sam marrocco | chief technical officer
ringside.cutters.flavor.picnic.moonlink

248 548 2500 w
248 910 3344 c

ringsidecreative.com