5V supply

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5V supply

Postby wtf62 on Mon Jun 09, 2008 9:50 am

Ho, hum. Why me ?

SAMrI is all built and it runs OK, so I thought I'd extend the capabilites by adding ultra-sonics, but it didn't work, and then I noticed that the 5V rail isn't 5V - it's about 3.5V. So I undid all my handywork with the SRF04 ultrasonic gizmo. Still 3.5V

So I isolated the voltage regulator - that's 5V OK
Connected the regulator back up, removed the PIC - still 3.5V
Removed the 11 links to the motor drive board - still 3.5V.
And that then doesn't leave a lot left connected

SAMrI works OK on 3.5v

I'm guessing the voltage regulator isn't working under load, so it's a stroll up to Maplins in a minute :|
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Re: 5V supply

Postby Techbotics on Mon Jun 09, 2008 11:25 am

Hi Mate

Sorry to hear you are having problems with your SAMrI.. all I can say is on both of mine the 5V rails on the PCB are well 5V..

I assume you have checked the output of your Battery pack and again from the regulator..? What do these show.. 9V from battey..? 3.5 from Regulator..? (then its probable faulty regulator which is unusual or faulty regulator installation) if you are getting 9V at battery and 5V at regulator but 3.5V at the prototype area then the problem lies elsewhere. Let me know how you get on.

Hope this helps

Damian
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Re: 5V supply

Postby Techbotics on Mon Jun 09, 2008 11:29 am

Apologies I notice you stated it was 5V from the regulator so thats working ok then I would assume.. please specify where you are seeing the 3.5V as opposed to 5V you expect on the PCB and I will check our's here..

How are you fitting the Ultrasonic sensor.. could you draw a scematic for me..?

Many Thanks

Damian
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Re: 5V supply

Postby wtf62 on Mon Jun 09, 2008 12:32 pm

I have replaced the regulator. It is OK now.

My basic machine now draws 68mA @ 5V when sitting idle running a while(1) do nothing loop

When I add on Q3 it goes up to 85mA @ 5V
Add in Q4 it goes up to 107mA @ 5V
Add in Q5 it goes up to 130mA

I think it must be close to the limit of the voltage regulator which is only rated at 100mA :shock:

I think that either I leave out the front sensors which don't seem to detect much over 4 inches away, or I fit a beefier regulator.
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Re: 5V supply

Postby slurp on Mon Jun 09, 2008 1:14 pm

wtf62 wrote:When I add on Q3 it goes up to 85mA @ 5V
Add in Q4 it goes up to 107mA @ 5V
Add in Q5 it goes up to 130mA

I think it must be close to the limit of the voltage regulator which is only rated at 100mA :shock:


Sounds like you should be looking for a regulator that give a much larger supply.... Low Drop Out (LDO) parts are usually better in thesse battery applications. :wink:

regards,
colin
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Re: 5V supply

Postby Techbotics on Mon Jun 09, 2008 1:43 pm

Thats interesting.. I've not seen this on mine yet but will take a look.. I am running 4 x QRD1114 sensors (not using the middle one) and 2 x GP2D12 sensors on one now so I would imagine I am well over.. I have some T0-220 package regulators kicking around so could swap to one of those if need be..

Re the QRD1114 sensors, you are correct they are a short range sensor intended to "fill" the blind spot in the GP2D12 / GP2D120 sensor's range.

Re LDO regulators, they are a good idea but the SAMrI battery pack is 4V above the regulated 5V at 9V and as such a LDO regulator should not be requied, a LDO will only come into its own if your battery is below 7V and by then your motor performance will seriously start to suffer.

Cheers

Damian

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Re: 5V supply

Postby JonHylands on Mon Jun 09, 2008 2:08 pm

Techbotics wrote:Thats interesting.. I've not seen this on mine yet but will take a look.. I am running 4 x QRD1114 sensors (not using the middle one) and 2 x GP2D12 sensors on one now so I would imagine I am well over.. I have some T0-220 package regulators kicking around so could swap to one of those if need be..

Re the QRD1114 sensors, you are correct they are a short range sensor intended to "fill" the blind spot in the GP2D12 / GP2D120 sensor's range.


First, each GP2D12 probably takes 100 mA running, and will peak at 250 or more at startup. You definitely need a one-amp regulator if you're using GP2D12 sensors.

The QRD1114 has a range of about 5-10mm, so it won't fill in the gap (100 mm) from the GP2D12. I use a Sharp IS471F for that...

- Jon
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Re: 5V supply

Postby Techbotics on Mon Jun 09, 2008 4:04 pm

JonHylands wrote:First, each GP2D12 probably takes 100 mA running, and will peak at 250 or more at startup. You definitely need a one-amp regulator if you're using GP2D12 sensors.


I guess its amazing mine ever worked at all then, but as Colin will attest both SAMrI were working with 2 x QRD1114 and 1 x GP2D12 at the ROTR event recently.. both managed to do this for something like 14 hours non stop too.

JonHylands wrote:The QRD1114 has a range of about 5-10mm, so it won't fill in the gap (100 mm) from the GP2D12. I use a Sharp IS471F for that...


I am going to move to GP2D120's so will only have 30-40mm to cover, however in current testing the QRD1114 seems to do fill the space no problem.. I would say I am getting results upto at least 50mm -70mm away from the sensor..

In my experiance this set up works well with GP2D12's and hopefully will be even better with GP2D120's..

Cheers

Damian

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