Relay's for 18x, Please Help

#1
Hello,
i am currently trying to make a proram for my project board, i have two problems.
The first is that my program will not download to my Picaxe 18x through my board, though it will download to the same chip on a picaxe project board that i purchased, this is a big program as i need to be programming a real time clock directly from a picaxe. I have checked all my circuit and it seems to meet the diagram provided by Picaxe.

The second is the realays on my board, i have three solid state relays, they are connected as follows, the relays + terminal is connected to +5v on the board, the - terminal is connect to a picaxe output. i have run the following program to the board and i have various different results.

Let pins = 0
main:
high 5
pause 1000
low 5
pause 1000
goto main

When this is programmed in, all three of my relays are turned on, then when i press the reset button on my board it turns them all of for a split second then two go back on and the one connected to pin 5 stays off for 1 second and then stays on forever.
can anyone please help me???
thanks
 
#2
Hi there.

Try putting a diode in line to prevent any feed back in to the chip, i had a simular thing happen when i had a feed back into an output on my 18X, the output would lock on till power was removed.
Also have you checked out what the voltage of the output is doing?

Robert
 
#3
Sounds like you have either a floating reset line or serin line.
Double check that you have the required pull-up on reset and pull-down on serin.
(the 10k/22k are NOT a potential divider).
How much current does the relay require to energise? Is that within the 20mA of the PICAXE output?
Should they have a series current limit resistor?
 
#4
Hey, thanks for your help.
I will try the diode, hopefully that will work as i had a previous board with the same relays but with transistors and diodes between the picaxe and the relay and that worked fine. Secondly, i am only a high school student and dont have the greater knowledge of electronics. But i think i may know the problem with my 4k7 pulldown resistor between +v and the reset pin, i think the problem may lay where i have put this connection betwwen the +v and reset pin after the download circuit, could this be my problem?
thanks
 
#5
Your last sentance gets a little muddled but there are indications that you may have reset wired the wrong way around.
To re-cap:-

Reset must be pulled high. Optional button to pull low.
Serin must be pulled low.

The way you wired the relays means that they will turn ON when the output goes low. Hence pins=0 should turn ON all relays.
When reset, the outputs go high impedance so all relays will turn off.

Your relays are solid-state devices and 'look like' an LED to the PICAXE. There is no coil and therefore no back emf so diodes should not be required.
If you can give a part number or pointer to their datasheet we can confirm if there will be any issues driving direct from a PICAXE output.
 
#6
hey, i have tried the same program without the let pins = 0 and i still get the same result. Here is a link to the relay i am using
http://www.altronics.com.au/index.asp?area=item&id=S4410
if you could look it over it would be appreciated
thanks
 
#7
mundic, can you tell us what project board you're using?

<i>...and the one connected to pin 5 stays off for 1 second and then stays on forever... </i>

Having seen your code and description of the connections, the relay should stay off for 1 second before operating. The 'High' command will set the PICAXE output to +5v, equal to the supply rail on the other side of the relay, so it won't operate until the pin goes low.) However, I don't understand why it should lock on.

Try disconnecting any loads that are connected to any of the relay's 'contacts'. Does the relay LED flash on and off every second?

Finally, output pin5 is leg 11, right?
 
#8
Indeed, the observed results seem to be correct for the software with the exception of the relay 'locking' on.
What load have you got on the relay?
It wouldn't be DC by any chance would it?
SS relays will 'lock' on until current is zero. With an AC load that happens every 20mS but with a DC load they will stay on forever.
 
#9
&quot;SS relays will 'lock' on until current is zero.&quot;
Is that always true BB?

I remember that Crydom do SS relays in Zero Cross and Random switch options.

The spec for the device being referred to doesn't define whether zero cross or random. It probably is and you're perfectly right. I just wanted to clarify that it may not be 100%.

It's probably made in the same factory that makes toys for Mattel.

I think Munic should post a schematic of his/her board.
AND try controlling the relays with a battery and switch and see what's going on.
If Munic has a mistake on the pcb then no-one else can spot it.
 
#10
The Altronics part that Mundic quoted is a Rayex RSR2ND-A24003 <A href='http://www.tme.pl/dok/a21/rsr2_series.pdf' Target=_Blank>External Web Link</a>
DC input control, AC output control, Zero On

Its intended for AC switching. But what does &quot;Zero On&quot; mean?
 
#11
Aha, so based on that, and assuming photo is accurate, then it is a Zero turn on. As you can see it is also available as random, but this requires readin the Data Sheet.

Zero on would same as zero cross, so that the on/off transition is nominally at zero volts of the AC cycle minimising sparkies. (As the Data Sheet says &quot;minize EMI/FRI&quot; - see even big companies can't spell!)
Great for min RFI etc but no good for phase power control eg dimmer.

Well done IP, top marks for detective work.
I guess sorting this out really requires more info from mundic.
The electron is in your court...
 
#12
my guess is that 'zero on' refers to the output switching on when the ac supply passes through the zero point of the sine wave (ac). its quite common to have triacs triggering at the zero crossing point
 
#13
Hello all,
your help is much appreciated, today (with some help from my teacher) i was able to solve both problems (download cable and relays) the following program works fine for them.

let pins = 224 &quot;switch off the relay pins
main:
low 5
pause 1000
high 5
pause 1000
goto main
 
#14
Mundic, it would be much clearer to write:-
let pins =%11100000 or
let pins =$E0

let pins = 224 does not make it obvious which outputs are on/off.


Dippy, I agree that it COULD be possible for a SS relay to turn off with current flowing but I've NEVER come across one nor do I know of a technology (besides power tranny) that could do it. (ie SSR, TRIAC always on above Imin).

Do you know of any that turn off?
 

premelec

Senior Member
#16
There are some SSRs that are FETs made conductive with LEDs inside [e.g. &quot;Photomos&quot;] - these are all low current as far as I know but can be Hi Voltage. Used in telephone switches and such... SCR TRIAC SSRs etc need to go to low current to turn off for sure! They latch on DC which sometimes is useful.... mostly annoying. :)
 
#17
When I was doing my electronics training (I have to admit, about 30 years ago) we were told, in passing, of an exciting new technology called &quot;Gate Turn Off Silicon Controlled Rectifier&quot;. It seems to have 'died the death': I haven't heard of it for years.

Dippy will hate me but I just Googled &quot;GTOSCR&quot; and &quot;GTO SCR&quot; and got 90,000 hits. So there may be a silicon DC switch in the form of a special SCR. I haven't checked the detail or the availability of the devices.

Edited by - inglewoodpete on 20/08/2007 06:04:16
 
#18
Au contraire IPete. You've proved how brilliantly useless Google is - just kidding, it has it's moments.

After BBs comments I did have a look round on Farnells site and see SSRs rated for AC and others specifically for DC, so I am 'briefed'.

The only AC/DC (cough!) devices I've seen are the signal level FET style output.

Anyway, I think mundic is sorted now. But it has been a useful thread and just shows that questioners should provide more information when posting, unless everyone enjoys chatting and/or spending time on tangents.
 
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