OKR-T/10, T/6, T/3 schematic circuit

[Breaktru]

Question for you, breaktru - in the OP diagram, you have a PTC fuse wired on Vin (this is also the way I wired the Raptor) - if the batts are put in backwards, are they protected from meltdown?

For the Raptor, the batts are not protected if put in backwards. 

Hmmm. You know mamu I put the fuse in as standard operating procedure. I never considered reverse battery protection.
Perhaps a diode would help as shown in the attached image below.

Diode D1 will not do anything, and will not waste power when power is applied correctly. However, if the polarity is reversed diode D1 conducts, and will trip the fuse.

[CraigHB]

That would actually limit reverse voltage to less than a volt for a Schottky rectifier, could be a benefit.  It will offload the rest of the circuit until the fuse trips.  Really good idea actually.  Kind of the same idea as using a diode for ESD protection.  You'll want a diode that can handle a few amps, a 5A diode can usually handle a 50A surge which should be adequate.  You'd want it to be good for a number of fault occurances.

Of course, if you're going to start adding components, a P-channel MOSFET in lieu of the diode would offer the best protection.  You get some loss with the transitor inline, but with prudent selection, it can be pretty negligible.

[mamu]

Well, I can confirm that with using the enable pin on the OKR-T10 the fuses (2x 5A in parallel) do not protect with reverse polarity.  The batts got hot hot hot and the insulation on the wires directly after the fuse melted and left another burn mark in my breadboard and this all happened within a few secs... 1001, 1002 - yeah that fast. 

I also tested wiring the fuses to the enable pin instead of Vin and got the same results as with the Raptor - there is reverse polarity protection for the batts, but not if you press the fire button.  If you press the fire button you get the same results as with the fuses wired to Vin.

I have no idea if using no pull-down resister and with an NC switch on the enable pin what's what as I did testing with a pull-down resister and an NO switch on the enable pin because I really want undervoltage protection for the batts. 

Full reverse polarity protection with batteries and circuit with using the same P-FET as with the Raptor.

This is the first time I've worked with the OKR-T10, so I wanted to experiment with the lowest ohm pull-down resister that would work in preventing auto-firing with and without using a zener diode on the enable pin.

Without the zener, you can go as high as 10K without causing auto-firing, but with the zener anything above 2K causes auto-firing.  1K prevents auto-firing with and without the zener, so that's the one I'm going to use with the OKR-T10.

And it makes sense for the 1K for the T10.  With the T3 a 100K resistor is needed, with the T6 a 10K resister is needed (decreased by a factor of 10 from the T3), and with the T10 a 1K is needed (decreased by a factor of 10 from the T6).

I got some red flashing LEDs recently and played with them when the FET was wired in and with the batts in backwards - kinda fun to see the red LED flashing when the batts are in backwards.    The LED doesn't light if the batts are in correctly.

And I put a 22uF 16v ceramic cap on the input (same part as for Raptor), but left off the output cap.  I've had such good results with longevity with all the mods I made with the T6 with caps, so figured a small input cap for buffering the converter's stress with repeated and frequent firing may help there.

Here's the wiring I did and will get it in a mod sometime when I have time...


SEE: UPDATED SCHEMATIC

[Breaktru]

Nice going mamu. Great work girl. Thank you for posting

[CraigHB]

Interesting stuff, I guess reverse polarity on the enable pin with these buck converters limits current not allowing the fuses to trip.  There's no skating on a transistor for reverse polarity protection when using the enable pin with them.

[mamu]

YW breaktru!

I'm wondering in what kind of situation will the fuse trip.  Maybe a disastrous short somewhere in the circuit or enable pin failure.  It's still curious that the enable pin limits current to the point that the batts aren't protected with reverse polarity.

[CraigHB]

This is the kind of thing exactly why you need to test stuff.  Just assuming it should work could lead to disasterous consequences.  There's no obvious reason why this would be the case (enable pin causes fuses not to trip), but there is always a level of FM (fricking magic) going on with electronics you have to deal with.  Sometimes things behave in unexpected ways. 

[mamu]

I hear ya about FM.   

It's good to sort these unexpected things out and figure out solutions.  After working with fuses and FETs I have a high regard for them and what they're doing to keep us safe.

[wreck]

I've built one mod using Breaktru's first schematic at the start of this thread. I'm looking to build a second, but I want to incorporate some sort of undervoltage protection. I still want to use a 3A pushbutton wired into pin 2.

This has been mentioned briefly in this thread, but not answered to a level I can understand 

How would I go about wiring a zener in if I am using a 3A pushbutton into pin 2?

Thanks again everyone.

[smami]

Hello to every one.
Does anyone know where to get these okr-t/10 chips in reasonable prices in Europe (Finland)? Because every where i tried to buy these they had 35+€ just for shipping which seems a bit much for 1 small 9$ chip.
Thanks.

[CraigHB]

You might try here;

http://fi.mouser.com/

Don't know if shipping will be cheap, but it should be a lot less than 35 Euros.

[Breaktru]

How about this: http://fi.farnell.com/murata-power-solutions/okr-t-10-w12-c/dc-dc-conv-non-iso-pol-1-o-p-50w/dp/1792312?ref=lookahead

http://www.arroweurope.com/countries/finland.html

Other parts: http://www.vekoy.com/

and: http://www.yeint.fi/

[smami]

Mouser is the cheapest one from what i have found, 20€ shippin and 2 chip minimum order.
(Farnell 50€ for 1 chip + shipping ) thanks for the help guys.

[CraigHB]

Twenty Euros is still awfully steep.  I'm not familiar with the mail options there, but here in the states I can ask Mouser to send things regular first class mail and they always do it when I ask them to.  I just put it in the "shipping instructions" text box.  It's actually a good service here with two or three day shipping, but it's limited to less than 12 oz (150g).  Super cheap though, like 2 USD.  Anyway, if there's a mail service option like that for you over there, you might try asking them to use it.  I'm sure a couple regulators are going to be plenty light enough.

[wreck]

Hi all.

I've been trying to get my head round how to incorporate a zener diode into the circuit for undervoltage protection.

I've currently got a layout set up on my bread board, and I've drawn a diagram of it below.



It is firing up fine... would someone be able to advice me whether the zener is wired in correctly and whether it will indeed work. I realised I have no idea if it will cut out without sitting here firing it till the batteries are drained :lol:

[CraigHB]

Plus and minus polarity is rather ambiguous for diodes so I'm not sure if your diode is wired right.  Diode polarity is normally identified by anode and cathode rather than plus or minus.  There should be a bar printed on the cathode side of the diode.  For a Zener, the bar side (cathode) should be connected to the high side or positive side of the connection.  That would be the switch in your case.  The opposite is true when using a diode as a rectifier which inverts plus and minus.

[wreck]

Thanks Craig, the cathode is indeed attached to my switch. Time to put it all together then

[Madyicstik]

If that is PCB with the tracers, it looks like it is not wired correctly. Like mamu said, only the resistor is in the circuit.
Look at the PCB board I show for the PTR08100. The wiring is the same. Just don't add the caps.



i want to use a prototype board on my okr build? will i follow this diagram , i do have caps on my build just wondering if it would be the same exact layout and cuts on the board?

[Breaktru]

Yes exactly the same except for the caps. I don't use caps on the OKR but some do (different values).

[mamu]

That's what's so nice about these various buck converters like the OKR, TI, Raptor - the wiring and external components required is all similar because the pins on all of them have the same function.

[CraigHB]

The ones with the pin headers are wired to be compatible with the linear regulators they're supposed to replace so they tend to have the same pin-outs.  You have to love stuff that's standard.  Though it can get you sometimes.  Power MOSFETs in SOIC and compatible packages are pretty much always pinned out the same and I made the assumption on some I changed out for better ones.  I almost sent the board design off to fab with the pin-out wrong.  Glad I caught that one, nothing like paying a chunk of change for some FR-4 drink coasters.

[Dropsomegears]

The OKR has onboard overcurrent protection, but no reverse polarity protection.   So, yes - fuses are necessary for safety.

I use these 2x in parallel for a 10A hold current for the OKR-T10: AGRF500-2.

You can go to octopart.com and enter the part number and find who sells them and who has the best price.

Hello all love this website soo much to learn. Quick noob question.  If the batteries are run in series. How does one run the fuses in parrallel?



Ben.

[Breaktru]

Hello all love this website soo much to learn. Quick noob question.  If the batteries are run in series. How does one run the fuses in parrallel?

Ben.

[Dropsomegears]

Thank you sir!!

Makes my life easier.

[jrweber02]

Whats the best method for cutting the line in yhe mini premade boards?

[davidlewallen]

How could I go about adding in reverse polarity protection to this?

[Breaktru]

How could I go about adding in reverse polarity protection to this?

Go to mamu's Reply #152 in this thread

[mamu]

I have tested both the smd P-FET that Craig recommends and the leaded P-FET sphearion is using.  There is no adverse effect on the input/output from the converter or voltage loss from either one - both do an excellent job of protecting the batts and circuitry for reverse polarity. 

Craig's is the better choice and has the lower RDS(on), but if you have trouble with soldering smd the leaded one will be a good substitute and is much easier to work with.

Here are the specs for each:
Si7157DP (smd)
Drain to Source Voltage (Vdss) - 20V
Current - Continuous Drain (Id) @ 25°C - 46.5A (Ta)
Rds On (Max) @ Id, Vgs - 1.6 mOhm @ 25A, 10V
Vgs(th) (Max) @ Id - 1.4V @ 250µA
Gate Charge (Qg) @ Vgs - 625nC @ 10V
Input Capacitance (Ciss) @ Vds - 22000pF @ 10V
Power - Max - 6.25W


SUP75P03-07-E3 (leaded)
Drain to Source Voltage (Vdss) - 30V
Current - Continuous Drain (Id) @ 25°C - 75A (Tc)
Rds On (Max) @ Id, Vgs - 7 mOhm @ 30A, 10V
Vgs(th) (Max) @ Id - 3V @ 250µA
Gate Charge (Qg) @ Vgs - 240nC @ 10V
Input Capacitance (Ciss) @ Vds - 9000pF @ 25V
Power - Max - 3.75W
Mounting Type - Through Hole

[mamu]

I'm going to have to do some more work with the zener and pull-down resister as the zener is not kicking in to shut off the converter.  I've tried the various zeners I have on hand and only the 6.8v zener is working for under voltage protection, but that's too high of a cutoff voltage.  I've tried the 5.6v, 6.0v, and 6.2v that I have and so far no go.

The 7.5K resister and zener work great for the Raptor for under-voltage protection, and also the 10K resister plus zener for the OKR-T6 work great, but either the resistor needs to be adjusted or I need to choose a different zener for the OKR-T10.  The problem is I can't go higher than 2K resister with the zener in line else the OKR auto-fires.

[Iamthebadass]

Mamu, try 1k for the T10.

That's what I have been using and it seems to work with a 5.6v Zener.

[mamu]

That's what I have wired - 1K resister with 5.6v or 6.0v zener (see post #152).

Do you have yours in a mod, badass?  Mine is breadboarded and the voltage is going uber low and not cutting off at what's expected.

Link to the zener you're using?

[Iamthebadass]

http://www.mouser.com/Search/ProductDetail.aspx?R=TZX5V6D-TRvirtualkey61370000virtualkey78-TZX5V6D

[mamu]

ok... got it solved.  Zener is working aok for low voltage cutoff. 

After shaking my head a bit I decided to buy some new breadboards and breadboarded the whole works on a new one. 

I'm going to toss out all my old breadboards.  After all this testing I've done with reverse polarity and diodes and FETs and fuses I've burnt some connections and have damaged the breadboards I have.     New start is nice.   

[Iamthebadass]

Awesome, so the 1k and Zener worked for you finally?

That is why I just mock everything up with solder, it can be a pain, but I have had some shoddy experiences with breadboards...

 

[CraigHB]

Yes, those breadboards can give you trouble.  You do need to replace them at some point, I probably need to replace the ones I have actually.  The connections wear out pretty fast on them.

One thing you can do to make breadboards more useful it to make small protoboards housing sub-circuits that plug in to the breadboards, but for anything with high current they're really not good for that.  There's a wire wrap method of breadboarding that's been around a lot longer than the more common solderless breadboarding which can handle currents a lot higher; http://en.wikipedia.org/wiki/Wire_wrap

[legionbornagain]

so after hooking everything up just like the schematic only thing is the resister is a 200 ohm with .5 watts, i found it at radio shack so should i get the right resister from digikey? the way that i have it wired it is only outputing .53 volts not sure what would be causing this but im slamming my head into a brick wall can someone chime in here and help me?

[mamu]

so after hooking everything up just like the schematic only thing is the resister is a 200 ohm with .5 watts, i found it at radio shack so should i get the right resister from digikey? the way that i have it wired it is only outputing .53 volts not sure what would be causing this but im slamming my head into a brick wall can someone chime in here and help me?

Yeah, a 220 ohm resister to bring the OKR back into spec.

Outputting .53 volts sounds like there's no pot or resister in line with pin 5.  Make sure you wired the resister and pot correctly to pin 5 and with the GND leg of the pot going to pin 3 and that there are no cold solder connections.

[david4500]

Was wondering if someone could please tell me what the amp draw on the batteries would be with them fully charged, inputting 8.4 volts to the okr-t/10, and the okr-t/10 outputting it's max of 6 volts. I'm a real dunderhead trying to wrap my head around all of this. From the spec sheet and what i've seen here, it looks like the amp draw to the input would be 4.53 amps @ 12 volts while outputting volts. Can someone confirm that this is correct? Would like to connect a slide switch to disconnect the battery to eliminate any drain, will be using remote on-off pin. Just trying to find a switch that would be in spec when wired to the positive from batteries. Thanks!

[CraigHB]

I've posted this on the forum before, but there's a simple way to find input current for a given output. 

Multiply your output current and voltage to get power.  Add 20% to that to cover losses then divide by input voltage to get input current. 

For example, a 1 Ohm atomizer with an applied voltage of 4V results in a current flow of 4 Amps.  Power is 16 Watts, 4A times 4V.  Add 20% for losses and that's 19.2 Watts.  For a worst case input voltage of 6V, you're looking at an input current of 3.2 Amps, 19.2W divided by 6V.

In reality, current demand is going to be a little lower since efficiency is usually around 90% and low voltage cutoff for the battery is somewhat above 6V, but it's not a bad idea to pad those numbers a bit.

[david4500]

Much appreciated reply, thanks!

[david4500]

any thoughts on the possibility of using a 500 ohm pot? if i calculated properly from the specs, it would lower the low voltage output to 2.23.

considering this as an option since there is a 500 ohm pot available that could be thread through a hole, secured with nut, and has a metal shaft. think it would be nice with a guitar knob attached.

alpha b500
http://www.ebay.com/itm/500-OHM-Linear-Taper-Rotary-Potentiometer-B500-Pot-/280672832335

[Breaktru]

any thoughts on the possibility of using a 500 ohm pot? if i calculated properly from the specs, it would lower the low voltage output to 2.23.

considering this as an option since there is a 500 ohm pot available that could be thread through a hole, secured with nut, and has a metal shaft. think it would be nice with a guitar knob attached.

alpha b500
http://www.ebay.com/itm/500-OHM-Linear-Taper-Rotary-Potentiometer-B500-Pot-/280672832335

Sure you can use it if you have the room to mount a 16mm base pot.
As far as the low end of the output voltage range goes, Only half of the pot wipe will be useful

[david4500]

In mamu's most recent diagram (http://breaktru.com/smf/index.php/topic,907.msg12662.html#msg12662), can two tact switches (replacing the on-off-on) be used to check either battery or output voltage? A mini voltmeter should be very low current draw enough for the tacts to handle correct? Can anything be done for safety in the event they were both simultaneously pressed?

[CraigHB]

Should be, but some tactiles have pretty low current limits.  You have to check the draw on the voltmeter and the limits on the particular switch you are using.   That voltmeter is probably going to draw around 50mA being the LED type.  LEDs have a relatively high current demand compared to circuits you typically use tactiles for.  Tactiles usually max out around 50mA, but they can be lower or higher depending on the part.

[mamu]

I'm not sure how you would wire an inline safety for not pressing both tacts at the same time.

Just takes that one time of being curious or not paying attention and *poof* the OKR is fried.  I tested the 2 tact setup back when I was designing Denali - got curious if the OKR would survive - it didn't. 

Maybe you'll figure out some way to do it though.

[wreck]

I've built up a new mod using the schematic I posted earlier

http://i.imgur.com/ZCjZQZw.jpg

(I've also got a voltmeter in it too)

I've run into a slight issue though, and was hoping one of you guys would be able to give me a bit of help.

The mod is cutting out when the batteries are only down to about 3.7-3.8V each. The display fades, and it stops firing properly, which I presume is the zener kicking in.

 Any ideas why the cut off is happening so early?

[M0n0]

I have a dumb question...so I've built a pass thru version only modifying breakthru's schem. By adding 12v n type plug to an okr-t/6 in hopes of running protanks as a pass thru (for juice bars) and I've fried two converters...well, two times now I have not recived signal to my atty out pins when the board is definately powered...I popped in a new 200 ohm pot and resistor, and new converter and got a great result on #2 chip until I plugged it in today and popped the cigarette adapter fuse followed by the same issue...I see the specs say 12v nominal so my assumption @ 1 ohm would be within the tolerences of my build...I did not add caps...but is that enough to be causing this???


Two chips down (I think) two on deck lol

[Breaktru]

Okay, let me get this straight. Chip #2 worked but the next day it blew a fuse. Sounds like you had the polarity correct or it wouldn't work the first day. Check your wiring and connections on the board output and on the 510. Also check the input and make sure there is no possible way the wiring or connections could short.
Close up photos w/ several views would be helpful.

What's the specs on the 12V source?

[M0n0]

Thanks for the reply and all the info you guys give..awesome!!

I'll have to double/triple check for the basics, I'm using a 10a bench power module (looks like a computer supply) and in the car a standard 12v cig adapter with a 5a fast blow on a 10a acessory terminal.
By theory I believe that would technically lower my overall amperage versus 7vdc...sound ok to you??

I'm gonna double check wiring, re-reading all the info I'm seeing different words stick out @ me as stuff I could have done wrong...

[M0n0]

Ok, I have;
-checked for continuity between ground and all v+ connections
-desoldier resistor/pot and check outputs (0-200 ohm on pot 220 ohm on resistor)
-jump fire button and hopscotch pins, loosing 12v on pin #4